Merge pull request #952 from xvhuan/feat/billing-ledger-decouple-usage-log-20260312

feat: 解耦计费正确性与 usage_logs 批量写压
2026-04-25 17:14:45 +08:00 · 2026-03-13 22:46:09 +08:00
parent 417861a48e 64b3f3cec1
commit 07bb2a5f3f
44 changed files with 4194 additions and 296 deletions
--- a/backend/internal/repository/dashboard_aggregation_repo.go
+++ b/backend/internal/repository/dashboard_aggregation_repo.go
@@ -17,6 +17,9 @@ type dashboardAggregationRepository struct {
 	sql sqlExecutor
 }

+const usageLogsCleanupBatchSize = 10000
+const usageBillingDedupCleanupBatchSize = 10000
+
 // NewDashboardAggregationRepository 创建仪表盘预聚合仓储。
 func NewDashboardAggregationRepository(sqlDB *sql.DB) service.DashboardAggregationRepository {
 	if sqlDB == nil {
@@ -42,6 +45,9 @@ func isPostgresDriver(db *sql.DB) bool {
 }

 func (r *dashboardAggregationRepository) AggregateRange(ctx context.Context, start, end time.Time) error {
+	if r == nil || r.sql == nil {
+		return nil
+	}
 	loc := timezone.Location()
 	startLocal := start.In(loc)
 	endLocal := end.In(loc)
@@ -61,6 +67,22 @@ func (r *dashboardAggregationRepository) AggregateRange(ctx context.Context, sta
 		dayEnd = dayEnd.Add(24 * time.Hour)
 	}

+	if db, ok := r.sql.(*sql.DB); ok {
+		tx, err := db.BeginTx(ctx, nil)
+		if err != nil {
+			return err
+		}
+		txRepo := newDashboardAggregationRepositoryWithSQL(tx)
+		if err := txRepo.aggregateRangeInTx(ctx, hourStart, hourEnd, dayStart, dayEnd); err != nil {
+			_ = tx.Rollback()
+			return err
+		}
+		return tx.Commit()
+	}
+	return r.aggregateRangeInTx(ctx, hourStart, hourEnd, dayStart, dayEnd)
+}
+
+func (r *dashboardAggregationRepository) aggregateRangeInTx(ctx context.Context, hourStart, hourEnd, dayStart, dayEnd time.Time) error {
 	// 以桶边界聚合，允许覆盖 end 所在桶的剩余区间。
 	if err := r.insertHourlyActiveUsers(ctx, hourStart, hourEnd); err != nil {
 		return err
@@ -195,8 +217,58 @@ func (r *dashboardAggregationRepository) CleanupUsageLogs(ctx context.Context, c
 	if isPartitioned {
 		return r.dropUsageLogsPartitions(ctx, cutoff)
 	}
-	_, err = r.sql.ExecContext(ctx, "DELETE FROM usage_logs WHERE created_at < $1", cutoff.UTC())
-	return err
+	for {
+		res, err := r.sql.ExecContext(ctx, `
+			WITH victims AS (
+				SELECT ctid
+				FROM usage_logs
+				WHERE created_at < $1
+				LIMIT $2
+			)
+			DELETE FROM usage_logs
+			WHERE ctid IN (SELECT ctid FROM victims)
+		`, cutoff.UTC(), usageLogsCleanupBatchSize)
+		if err != nil {
+			return err
+		}
+		affected, err := res.RowsAffected()
+		if err != nil {
+			return err
+		}
+		if affected < usageLogsCleanupBatchSize {
+			return nil
+		}
+	}
+}
+
+func (r *dashboardAggregationRepository) CleanupUsageBillingDedup(ctx context.Context, cutoff time.Time) error {
+	for {
+		res, err := r.sql.ExecContext(ctx, `
+			WITH victims AS (
+				SELECT ctid, request_id, api_key_id, request_fingerprint, created_at
+				FROM usage_billing_dedup
+				WHERE created_at < $1
+				LIMIT $2
+			), archived AS (
+				INSERT INTO usage_billing_dedup_archive (request_id, api_key_id, request_fingerprint, created_at)
+				SELECT request_id, api_key_id, request_fingerprint, created_at
+				FROM victims
+				ON CONFLICT (request_id, api_key_id) DO NOTHING
+			)
+			DELETE FROM usage_billing_dedup
+			WHERE ctid IN (SELECT ctid FROM victims)
+		`, cutoff.UTC(), usageBillingDedupCleanupBatchSize)
+		if err != nil {
+			return err
+		}
+		affected, err := res.RowsAffected()
+		if err != nil {
+			return err
+		}
+		if affected < usageBillingDedupCleanupBatchSize {
+			return nil
+		}
+	}
 }

 func (r *dashboardAggregationRepository) EnsureUsageLogsPartitions(ctx context.Context, now time.Time) error {
--- a/backend/internal/repository/fixtures_integration_test.go
+++ b/backend/internal/repository/fixtures_integration_test.go
@@ -262,6 +262,42 @@ func mustCreateApiKey(t *testing.T, client *dbent.Client, k *service.APIKey) *se
 		SetKey(k.Key).
 		SetName(k.Name).
 		SetStatus(k.Status)
+	if k.Quota != 0 {
+		create.SetQuota(k.Quota)
+	}
+	if k.QuotaUsed != 0 {
+		create.SetQuotaUsed(k.QuotaUsed)
+	}
+	if k.RateLimit5h != 0 {
+		create.SetRateLimit5h(k.RateLimit5h)
+	}
+	if k.RateLimit1d != 0 {
+		create.SetRateLimit1d(k.RateLimit1d)
+	}
+	if k.RateLimit7d != 0 {
+		create.SetRateLimit7d(k.RateLimit7d)
+	}
+	if k.Usage5h != 0 {
+		create.SetUsage5h(k.Usage5h)
+	}
+	if k.Usage1d != 0 {
+		create.SetUsage1d(k.Usage1d)
+	}
+	if k.Usage7d != 0 {
+		create.SetUsage7d(k.Usage7d)
+	}
+	if k.Window5hStart != nil {
+		create.SetWindow5hStart(*k.Window5hStart)
+	}
+	if k.Window1dStart != nil {
+		create.SetWindow1dStart(*k.Window1dStart)
+	}
+	if k.Window7dStart != nil {
+		create.SetWindow7dStart(*k.Window7dStart)
+	}
+	if k.ExpiresAt != nil {
+		create.SetExpiresAt(*k.ExpiresAt)
+	}
 	if k.GroupID != nil {
 		create.SetGroupID(*k.GroupID)
 	}
--- a/backend/internal/repository/migrations_schema_integration_test.go
+++ b/backend/internal/repository/migrations_schema_integration_test.go
@@ -45,6 +45,20 @@ func TestMigrationsRunner_IsIdempotent_AndSchemaIsUpToDate(t *testing.T) {
 	requireColumn(t, tx, "usage_logs", "request_type", "smallint", 0, false)
 	requireColumn(t, tx, "usage_logs", "openai_ws_mode", "boolean", 0, false)

+	// usage_billing_dedup: billing idempotency narrow table
+	var usageBillingDedupRegclass sql.NullString
+	require.NoError(t, tx.QueryRowContext(context.Background(), "SELECT to_regclass('public.usage_billing_dedup')").Scan(&usageBillingDedupRegclass))
+	require.True(t, usageBillingDedupRegclass.Valid, "expected usage_billing_dedup table to exist")
+	requireColumn(t, tx, "usage_billing_dedup", "request_fingerprint", "character varying", 64, false)
+	requireIndex(t, tx, "usage_billing_dedup", "idx_usage_billing_dedup_request_api_key")
+	requireIndex(t, tx, "usage_billing_dedup", "idx_usage_billing_dedup_created_at_brin")
+
+	var usageBillingDedupArchiveRegclass sql.NullString
+	require.NoError(t, tx.QueryRowContext(context.Background(), "SELECT to_regclass('public.usage_billing_dedup_archive')").Scan(&usageBillingDedupArchiveRegclass))
+	require.True(t, usageBillingDedupArchiveRegclass.Valid, "expected usage_billing_dedup_archive table to exist")
+	requireColumn(t, tx, "usage_billing_dedup_archive", "request_fingerprint", "character varying", 64, false)
+	requireIndex(t, tx, "usage_billing_dedup_archive", "usage_billing_dedup_archive_pkey")
+
 	// settings table should exist
 	var settingsRegclass sql.NullString
 	require.NoError(t, tx.QueryRowContext(context.Background(), "SELECT to_regclass('public.settings')").Scan(&settingsRegclass))
@@ -75,6 +89,23 @@ func TestMigrationsRunner_IsIdempotent_AndSchemaIsUpToDate(t *testing.T) {
 	requireColumn(t, tx, "user_allowed_groups", "created_at", "timestamp with time zone", 0, false)
 }

+func requireIndex(t *testing.T, tx *sql.Tx, table, index string) {
+	t.Helper()
+
+	var exists bool
+	err := tx.QueryRowContext(context.Background(), `
+SELECT EXISTS (
+	SELECT 1
+	FROM pg_indexes
+	WHERE schemaname = 'public'
+	  AND tablename = $1
+	  AND indexname = $2
+)
+`, table, index).Scan(&exists)
+	require.NoError(t, err, "query pg_indexes for %s.%s", table, index)
+	require.True(t, exists, "expected index %s on %s", index, table)
+}
+
 func requireColumn(t *testing.T, tx *sql.Tx, table, column, dataType string, maxLen int, nullable bool) {
 	t.Helper()

--- a/backend/internal/repository/usage_billing_repo.go
+++ b/backend/internal/repository/usage_billing_repo.go
@@ -0,0 +1,308 @@
+package repository
+
+import (
+	"context"
+	"database/sql"
+	"errors"
+	"strings"
+
+	dbent "github.com/Wei-Shaw/sub2api/ent"
+	"github.com/Wei-Shaw/sub2api/internal/pkg/logger"
+	"github.com/Wei-Shaw/sub2api/internal/service"
+)
+
+type usageBillingRepository struct {
+	db *sql.DB
+}
+
+func NewUsageBillingRepository(_ *dbent.Client, sqlDB *sql.DB) service.UsageBillingRepository {
+	return &usageBillingRepository{db: sqlDB}
+}
+
+func (r *usageBillingRepository) Apply(ctx context.Context, cmd *service.UsageBillingCommand) (_ *service.UsageBillingApplyResult, err error) {
+	if cmd == nil {
+		return &service.UsageBillingApplyResult{}, nil
+	}
+	if r == nil || r.db == nil {
+		return nil, errors.New("usage billing repository db is nil")
+	}
+
+	cmd.Normalize()
+	if cmd.RequestID == "" {
+		return nil, service.ErrUsageBillingRequestIDRequired
+	}
+
+	tx, err := r.db.BeginTx(ctx, nil)
+	if err != nil {
+		return nil, err
+	}
+	defer func() {
+		if tx != nil {
+			_ = tx.Rollback()
+		}
+	}()
+
+	applied, err := r.claimUsageBillingKey(ctx, tx, cmd)
+	if err != nil {
+		return nil, err
+	}
+	if !applied {
+		return &service.UsageBillingApplyResult{Applied: false}, nil
+	}
+
+	result := &service.UsageBillingApplyResult{Applied: true}
+	if err := r.applyUsageBillingEffects(ctx, tx, cmd, result); err != nil {
+		return nil, err
+	}
+
+	if err := tx.Commit(); err != nil {
+		return nil, err
+	}
+	tx = nil
+	return result, nil
+}
+
+func (r *usageBillingRepository) claimUsageBillingKey(ctx context.Context, tx *sql.Tx, cmd *service.UsageBillingCommand) (bool, error) {
+	var id int64
+	err := tx.QueryRowContext(ctx, `
+		INSERT INTO usage_billing_dedup (request_id, api_key_id, request_fingerprint)
+		VALUES ($1, $2, $3)
+		ON CONFLICT (request_id, api_key_id) DO NOTHING
+		RETURNING id
+	`, cmd.RequestID, cmd.APIKeyID, cmd.RequestFingerprint).Scan(&id)
+	if errors.Is(err, sql.ErrNoRows) {
+		var existingFingerprint string
+		if err := tx.QueryRowContext(ctx, `
+			SELECT request_fingerprint
+			FROM usage_billing_dedup
+			WHERE request_id = $1 AND api_key_id = $2
+		`, cmd.RequestID, cmd.APIKeyID).Scan(&existingFingerprint); err != nil {
+			return false, err
+		}
+		if strings.TrimSpace(existingFingerprint) != strings.TrimSpace(cmd.RequestFingerprint) {
+			return false, service.ErrUsageBillingRequestConflict
+		}
+		return false, nil
+	}
+	if err != nil {
+		return false, err
+	}
+	var archivedFingerprint string
+	err = tx.QueryRowContext(ctx, `
+		SELECT request_fingerprint
+		FROM usage_billing_dedup_archive
+		WHERE request_id = $1 AND api_key_id = $2
+	`, cmd.RequestID, cmd.APIKeyID).Scan(&archivedFingerprint)
+	if err == nil {
+		if strings.TrimSpace(archivedFingerprint) != strings.TrimSpace(cmd.RequestFingerprint) {
+			return false, service.ErrUsageBillingRequestConflict
+		}
+		return false, nil
+	}
+	if !errors.Is(err, sql.ErrNoRows) {
+		return false, err
+	}
+	return true, nil
+}
+
+func (r *usageBillingRepository) applyUsageBillingEffects(ctx context.Context, tx *sql.Tx, cmd *service.UsageBillingCommand, result *service.UsageBillingApplyResult) error {
+	if cmd.SubscriptionCost > 0 && cmd.SubscriptionID != nil {
+		if err := incrementUsageBillingSubscription(ctx, tx, *cmd.SubscriptionID, cmd.SubscriptionCost); err != nil {
+			return err
+		}
+	}
+
+	if cmd.BalanceCost > 0 {
+		if err := deductUsageBillingBalance(ctx, tx, cmd.UserID, cmd.BalanceCost); err != nil {
+			return err
+		}
+	}
+
+	if cmd.APIKeyQuotaCost > 0 {
+		exhausted, err := incrementUsageBillingAPIKeyQuota(ctx, tx, cmd.APIKeyID, cmd.APIKeyQuotaCost)
+		if err != nil {
+			return err
+		}
+		result.APIKeyQuotaExhausted = exhausted
+	}
+
+	if cmd.APIKeyRateLimitCost > 0 {
+		if err := incrementUsageBillingAPIKeyRateLimit(ctx, tx, cmd.APIKeyID, cmd.APIKeyRateLimitCost); err != nil {
+			return err
+		}
+	}
+
+	if cmd.AccountQuotaCost > 0 && strings.EqualFold(cmd.AccountType, service.AccountTypeAPIKey) {
+		if err := incrementUsageBillingAccountQuota(ctx, tx, cmd.AccountID, cmd.AccountQuotaCost); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func incrementUsageBillingSubscription(ctx context.Context, tx *sql.Tx, subscriptionID int64, costUSD float64) error {
+	const updateSQL = `
+		UPDATE user_subscriptions us
+		SET
+			daily_usage_usd = us.daily_usage_usd + $1,
+			weekly_usage_usd = us.weekly_usage_usd + $1,
+			monthly_usage_usd = us.monthly_usage_usd + $1,
+			updated_at = NOW()
+		FROM groups g
+		WHERE us.id = $2
+			AND us.deleted_at IS NULL
+			AND us.group_id = g.id
+			AND g.deleted_at IS NULL
+	`
+	res, err := tx.ExecContext(ctx, updateSQL, costUSD, subscriptionID)
+	if err != nil {
+		return err
+	}
+	affected, err := res.RowsAffected()
+	if err != nil {
+		return err
+	}
+	if affected > 0 {
+		return nil
+	}
+	return service.ErrSubscriptionNotFound
+}
+
+func deductUsageBillingBalance(ctx context.Context, tx *sql.Tx, userID int64, amount float64) error {
+	res, err := tx.ExecContext(ctx, `
+		UPDATE users
+		SET balance = balance - $1,
+			updated_at = NOW()
+		WHERE id = $2 AND deleted_at IS NULL
+	`, amount, userID)
+	if err != nil {
+		return err
+	}
+	affected, err := res.RowsAffected()
+	if err != nil {
+		return err
+	}
+	if affected > 0 {
+		return nil
+	}
+	return service.ErrUserNotFound
+}
+
+func incrementUsageBillingAPIKeyQuota(ctx context.Context, tx *sql.Tx, apiKeyID int64, amount float64) (bool, error) {
+	var exhausted bool
+	err := tx.QueryRowContext(ctx, `
+		UPDATE api_keys
+		SET quota_used = quota_used + $1,
+			status = CASE
+				WHEN quota > 0
+					AND status = $3
+					AND quota_used < quota
+					AND quota_used + $1 >= quota
+				THEN $4
+				ELSE status
+			END,
+			updated_at = NOW()
+		WHERE id = $2 AND deleted_at IS NULL
+		RETURNING quota > 0 AND quota_used >= quota AND quota_used - $1 < quota
+	`, amount, apiKeyID, service.StatusAPIKeyActive, service.StatusAPIKeyQuotaExhausted).Scan(&exhausted)
+	if errors.Is(err, sql.ErrNoRows) {
+		return false, service.ErrAPIKeyNotFound
+	}
+	if err != nil {
+		return false, err
+	}
+	return exhausted, nil
+}
+
+func incrementUsageBillingAPIKeyRateLimit(ctx context.Context, tx *sql.Tx, apiKeyID int64, cost float64) error {
+	res, err := tx.ExecContext(ctx, `
+		UPDATE api_keys SET
+			usage_5h = CASE WHEN window_5h_start IS NOT NULL AND window_5h_start + INTERVAL '5 hours' <= NOW() THEN $1 ELSE usage_5h + $1 END,
+			usage_1d = CASE WHEN window_1d_start IS NOT NULL AND window_1d_start + INTERVAL '24 hours' <= NOW() THEN $1 ELSE usage_1d + $1 END,
+			usage_7d = CASE WHEN window_7d_start IS NOT NULL AND window_7d_start + INTERVAL '7 days' <= NOW() THEN $1 ELSE usage_7d + $1 END,
+			window_5h_start = CASE WHEN window_5h_start IS NULL OR window_5h_start + INTERVAL '5 hours' <= NOW() THEN NOW() ELSE window_5h_start END,
+			window_1d_start = CASE WHEN window_1d_start IS NULL OR window_1d_start + INTERVAL '24 hours' <= NOW() THEN date_trunc('day', NOW()) ELSE window_1d_start END,
+			window_7d_start = CASE WHEN window_7d_start IS NULL OR window_7d_start + INTERVAL '7 days' <= NOW() THEN date_trunc('day', NOW()) ELSE window_7d_start END,
+			updated_at = NOW()
+		WHERE id = $2 AND deleted_at IS NULL
+	`, cost, apiKeyID)
+	if err != nil {
+		return err
+	}
+	affected, err := res.RowsAffected()
+	if err != nil {
+		return err
+	}
+	if affected == 0 {
+		return service.ErrAPIKeyNotFound
+	}
+	return nil
+}
+
+func incrementUsageBillingAccountQuota(ctx context.Context, tx *sql.Tx, accountID int64, amount float64) error {
+	rows, err := tx.QueryContext(ctx,
+		`UPDATE accounts SET extra = (
+			COALESCE(extra, '{}'::jsonb)
+			|| jsonb_build_object('quota_used', COALESCE((extra->>'quota_used')::numeric, 0) + $1)
+			|| CASE WHEN COALESCE((extra->>'quota_daily_limit')::numeric, 0) > 0 THEN
+				jsonb_build_object(
+					'quota_daily_used',
+					CASE WHEN COALESCE((extra->>'quota_daily_start')::timestamptz, '1970-01-01'::timestamptz)
+						+ '24 hours'::interval <= NOW()
+					THEN $1
+					ELSE COALESCE((extra->>'quota_daily_used')::numeric, 0) + $1 END,
+					'quota_daily_start',
+					CASE WHEN COALESCE((extra->>'quota_daily_start')::timestamptz, '1970-01-01'::timestamptz)
+						+ '24 hours'::interval <= NOW()
+					THEN `+nowUTC+`
+					ELSE COALESCE(extra->>'quota_daily_start', `+nowUTC+`) END
+				)
+			ELSE '{}'::jsonb END
+			|| CASE WHEN COALESCE((extra->>'quota_weekly_limit')::numeric, 0) > 0 THEN
+				jsonb_build_object(
+					'quota_weekly_used',
+					CASE WHEN COALESCE((extra->>'quota_weekly_start')::timestamptz, '1970-01-01'::timestamptz)
+						+ '168 hours'::interval <= NOW()
+					THEN $1
+					ELSE COALESCE((extra->>'quota_weekly_used')::numeric, 0) + $1 END,
+					'quota_weekly_start',
+					CASE WHEN COALESCE((extra->>'quota_weekly_start')::timestamptz, '1970-01-01'::timestamptz)
+						+ '168 hours'::interval <= NOW()
+					THEN `+nowUTC+`
+					ELSE COALESCE(extra->>'quota_weekly_start', `+nowUTC+`) END
+				)
+			ELSE '{}'::jsonb END
+		), updated_at = NOW()
+		WHERE id = $2 AND deleted_at IS NULL
+		RETURNING
+			COALESCE((extra->>'quota_used')::numeric, 0),
+			COALESCE((extra->>'quota_limit')::numeric, 0)`,
+		amount, accountID)
+	if err != nil {
+		return err
+	}
+	defer func() { _ = rows.Close() }()
+
+	var newUsed, limit float64
+	if rows.Next() {
+		if err := rows.Scan(&newUsed, &limit); err != nil {
+			return err
+		}
+	} else {
+		if err := rows.Err(); err != nil {
+			return err
+		}
+		return service.ErrAccountNotFound
+	}
+	if err := rows.Err(); err != nil {
+		return err
+	}
+	if limit > 0 && newUsed >= limit && (newUsed-amount) < limit {
+		if err := enqueueSchedulerOutbox(ctx, tx, service.SchedulerOutboxEventAccountChanged, &accountID, nil, nil); err != nil {
+			logger.LegacyPrintf("repository.usage_billing", "[SchedulerOutbox] enqueue quota exceeded failed: account=%d err=%v", accountID, err)
+			return err
+		}
+	}
+	return nil
+}
--- a/backend/internal/repository/usage_billing_repo_integration_test.go
+++ b/backend/internal/repository/usage_billing_repo_integration_test.go
@@ -0,0 +1,279 @@
+//go:build integration
+
+package repository
+
+import (
+	"context"
+	"fmt"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/google/uuid"
+	"github.com/stretchr/testify/require"
+
+	"github.com/Wei-Shaw/sub2api/internal/service"
+)
+
+func TestUsageBillingRepositoryApply_DeduplicatesBalanceBilling(t *testing.T) {
+	ctx := context.Background()
+	client := testEntClient(t)
+	repo := NewUsageBillingRepository(client, integrationDB)
+
+	user := mustCreateUser(t, client, &service.User{
+		Email:        fmt.Sprintf("usage-billing-user-%d@example.com", time.Now().UnixNano()),
+		PasswordHash: "hash",
+		Balance:      100,
+	})
+	apiKey := mustCreateApiKey(t, client, &service.APIKey{
+		UserID: user.ID,
+		Key:    "sk-usage-billing-" + uuid.NewString(),
+		Name:   "billing",
+		Quota:  1,
+	})
+	account := mustCreateAccount(t, client, &service.Account{
+		Name: "usage-billing-account-" + uuid.NewString(),
+		Type: service.AccountTypeAPIKey,
+	})
+
+	requestID := uuid.NewString()
+	cmd := &service.UsageBillingCommand{
+		RequestID:           requestID,
+		APIKeyID:            apiKey.ID,
+		UserID:              user.ID,
+		AccountID:           account.ID,
+		AccountType:         service.AccountTypeAPIKey,
+		BalanceCost:         1.25,
+		APIKeyQuotaCost:     1.25,
+		APIKeyRateLimitCost: 1.25,
+	}
+
+	result1, err := repo.Apply(ctx, cmd)
+	require.NoError(t, err)
+	require.NotNil(t, result1)
+	require.True(t, result1.Applied)
+	require.True(t, result1.APIKeyQuotaExhausted)
+
+	result2, err := repo.Apply(ctx, cmd)
+	require.NoError(t, err)
+	require.NotNil(t, result2)
+	require.False(t, result2.Applied)
+
+	var balance float64
+	require.NoError(t, integrationDB.QueryRowContext(ctx, "SELECT balance FROM users WHERE id = $1", user.ID).Scan(&balance))
+	require.InDelta(t, 98.75, balance, 0.000001)
+
+	var quotaUsed float64
+	require.NoError(t, integrationDB.QueryRowContext(ctx, "SELECT quota_used FROM api_keys WHERE id = $1", apiKey.ID).Scan(&quotaUsed))
+	require.InDelta(t, 1.25, quotaUsed, 0.000001)
+
+	var usage5h float64
+	require.NoError(t, integrationDB.QueryRowContext(ctx, "SELECT usage_5h FROM api_keys WHERE id = $1", apiKey.ID).Scan(&usage5h))
+	require.InDelta(t, 1.25, usage5h, 0.000001)
+
+	var status string
+	require.NoError(t, integrationDB.QueryRowContext(ctx, "SELECT status FROM api_keys WHERE id = $1", apiKey.ID).Scan(&status))
+	require.Equal(t, service.StatusAPIKeyQuotaExhausted, status)
+
+	var dedupCount int
+	require.NoError(t, integrationDB.QueryRowContext(ctx, "SELECT COUNT(*) FROM usage_billing_dedup WHERE request_id = $1 AND api_key_id = $2", requestID, apiKey.ID).Scan(&dedupCount))
+	require.Equal(t, 1, dedupCount)
+}
+
+func TestUsageBillingRepositoryApply_DeduplicatesSubscriptionBilling(t *testing.T) {
+	ctx := context.Background()
+	client := testEntClient(t)
+	repo := NewUsageBillingRepository(client, integrationDB)
+
+	user := mustCreateUser(t, client, &service.User{
+		Email:        fmt.Sprintf("usage-billing-sub-user-%d@example.com", time.Now().UnixNano()),
+		PasswordHash: "hash",
+	})
+	group := mustCreateGroup(t, client, &service.Group{
+		Name:             "usage-billing-group-" + uuid.NewString(),
+		Platform:         service.PlatformAnthropic,
+		SubscriptionType: service.SubscriptionTypeSubscription,
+	})
+	apiKey := mustCreateApiKey(t, client, &service.APIKey{
+		UserID:  user.ID,
+		GroupID: &group.ID,
+		Key:     "sk-usage-billing-sub-" + uuid.NewString(),
+		Name:    "billing-sub",
+	})
+	subscription := mustCreateSubscription(t, client, &service.UserSubscription{
+		UserID:  user.ID,
+		GroupID: group.ID,
+	})
+
+	requestID := uuid.NewString()
+	cmd := &service.UsageBillingCommand{
+		RequestID:        requestID,
+		APIKeyID:         apiKey.ID,
+		UserID:           user.ID,
+		AccountID:        0,
+		SubscriptionID:   &subscription.ID,
+		SubscriptionCost: 2.5,
+	}
+
+	result1, err := repo.Apply(ctx, cmd)
+	require.NoError(t, err)
+	require.True(t, result1.Applied)
+
+	result2, err := repo.Apply(ctx, cmd)
+	require.NoError(t, err)
+	require.False(t, result2.Applied)
+
+	var dailyUsage float64
+	require.NoError(t, integrationDB.QueryRowContext(ctx, "SELECT daily_usage_usd FROM user_subscriptions WHERE id = $1", subscription.ID).Scan(&dailyUsage))
+	require.InDelta(t, 2.5, dailyUsage, 0.000001)
+}
+
+func TestUsageBillingRepositoryApply_RequestFingerprintConflict(t *testing.T) {
+	ctx := context.Background()
+	client := testEntClient(t)
+	repo := NewUsageBillingRepository(client, integrationDB)
+
+	user := mustCreateUser(t, client, &service.User{
+		Email:        fmt.Sprintf("usage-billing-conflict-user-%d@example.com", time.Now().UnixNano()),
+		PasswordHash: "hash",
+		Balance:      100,
+	})
+	apiKey := mustCreateApiKey(t, client, &service.APIKey{
+		UserID: user.ID,
+		Key:    "sk-usage-billing-conflict-" + uuid.NewString(),
+		Name:   "billing-conflict",
+	})
+
+	requestID := uuid.NewString()
+	_, err := repo.Apply(ctx, &service.UsageBillingCommand{
+		RequestID:   requestID,
+		APIKeyID:    apiKey.ID,
+		UserID:      user.ID,
+		BalanceCost: 1.25,
+	})
+	require.NoError(t, err)
+
+	_, err = repo.Apply(ctx, &service.UsageBillingCommand{
+		RequestID:   requestID,
+		APIKeyID:    apiKey.ID,
+		UserID:      user.ID,
+		BalanceCost: 2.50,
+	})
+	require.ErrorIs(t, err, service.ErrUsageBillingRequestConflict)
+}
+
+func TestUsageBillingRepositoryApply_UpdatesAccountQuota(t *testing.T) {
+	ctx := context.Background()
+	client := testEntClient(t)
+	repo := NewUsageBillingRepository(client, integrationDB)
+
+	user := mustCreateUser(t, client, &service.User{
+		Email:        fmt.Sprintf("usage-billing-account-user-%d@example.com", time.Now().UnixNano()),
+		PasswordHash: "hash",
+	})
+	apiKey := mustCreateApiKey(t, client, &service.APIKey{
+		UserID: user.ID,
+		Key:    "sk-usage-billing-account-" + uuid.NewString(),
+		Name:   "billing-account",
+	})
+	account := mustCreateAccount(t, client, &service.Account{
+		Name: "usage-billing-account-quota-" + uuid.NewString(),
+		Type: service.AccountTypeAPIKey,
+		Extra: map[string]any{
+			"quota_limit": 100.0,
+		},
+	})
+
+	_, err := repo.Apply(ctx, &service.UsageBillingCommand{
+		RequestID:        uuid.NewString(),
+		APIKeyID:         apiKey.ID,
+		UserID:           user.ID,
+		AccountID:        account.ID,
+		AccountType:      service.AccountTypeAPIKey,
+		AccountQuotaCost: 3.5,
+	})
+	require.NoError(t, err)
+
+	var quotaUsed float64
+	require.NoError(t, integrationDB.QueryRowContext(ctx, "SELECT COALESCE((extra->>'quota_used')::numeric, 0) FROM accounts WHERE id = $1", account.ID).Scan(&quotaUsed))
+	require.InDelta(t, 3.5, quotaUsed, 0.000001)
+}
+
+func TestDashboardAggregationRepositoryCleanupUsageBillingDedup_BatchDeletesOldRows(t *testing.T) {
+	ctx := context.Background()
+	repo := newDashboardAggregationRepositoryWithSQL(integrationDB)
+
+	oldRequestID := "dedup-old-" + uuid.NewString()
+	newRequestID := "dedup-new-" + uuid.NewString()
+	oldCreatedAt := time.Now().UTC().AddDate(0, 0, -400)
+	newCreatedAt := time.Now().UTC().Add(-time.Hour)
+
+	_, err := integrationDB.ExecContext(ctx, `
+		INSERT INTO usage_billing_dedup (request_id, api_key_id, request_fingerprint, created_at)
+		VALUES ($1, 1, $2, $3), ($4, 1, $5, $6)
+	`,
+		oldRequestID, strings.Repeat("a", 64), oldCreatedAt,
+		newRequestID, strings.Repeat("b", 64), newCreatedAt,
+	)
+	require.NoError(t, err)
+
+	require.NoError(t, repo.CleanupUsageBillingDedup(ctx, time.Now().UTC().AddDate(0, 0, -365)))
+
+	var oldCount int
+	require.NoError(t, integrationDB.QueryRowContext(ctx, "SELECT COUNT(*) FROM usage_billing_dedup WHERE request_id = $1", oldRequestID).Scan(&oldCount))
+	require.Equal(t, 0, oldCount)
+
+	var newCount int
+	require.NoError(t, integrationDB.QueryRowContext(ctx, "SELECT COUNT(*) FROM usage_billing_dedup WHERE request_id = $1", newRequestID).Scan(&newCount))
+	require.Equal(t, 1, newCount)
+
+	var archivedCount int
+	require.NoError(t, integrationDB.QueryRowContext(ctx, "SELECT COUNT(*) FROM usage_billing_dedup_archive WHERE request_id = $1", oldRequestID).Scan(&archivedCount))
+	require.Equal(t, 1, archivedCount)
+}
+
+func TestUsageBillingRepositoryApply_DeduplicatesAgainstArchivedKey(t *testing.T) {
+	ctx := context.Background()
+	client := testEntClient(t)
+	repo := NewUsageBillingRepository(client, integrationDB)
+	aggRepo := newDashboardAggregationRepositoryWithSQL(integrationDB)
+
+	user := mustCreateUser(t, client, &service.User{
+		Email:        fmt.Sprintf("usage-billing-archive-user-%d@example.com", time.Now().UnixNano()),
+		PasswordHash: "hash",
+		Balance:      100,
+	})
+	apiKey := mustCreateApiKey(t, client, &service.APIKey{
+		UserID: user.ID,
+		Key:    "sk-usage-billing-archive-" + uuid.NewString(),
+		Name:   "billing-archive",
+	})
+
+	requestID := uuid.NewString()
+	cmd := &service.UsageBillingCommand{
+		RequestID:   requestID,
+		APIKeyID:    apiKey.ID,
+		UserID:      user.ID,
+		BalanceCost: 1.25,
+	}
+
+	result1, err := repo.Apply(ctx, cmd)
+	require.NoError(t, err)
+	require.True(t, result1.Applied)
+
+	_, err = integrationDB.ExecContext(ctx, `
+		UPDATE usage_billing_dedup
+		SET created_at = $1
+		WHERE request_id = $2 AND api_key_id = $3
+	`, time.Now().UTC().AddDate(0, 0, -400), requestID, apiKey.ID)
+	require.NoError(t, err)
+	require.NoError(t, aggRepo.CleanupUsageBillingDedup(ctx, time.Now().UTC().AddDate(0, 0, -365)))
+
+	result2, err := repo.Apply(ctx, cmd)
+	require.NoError(t, err)
+	require.False(t, result2.Applied)
+
+	var balance float64
+	require.NoError(t, integrationDB.QueryRowContext(ctx, "SELECT balance FROM users WHERE id = $1", user.ID).Scan(&balance))
+	require.InDelta(t, 98.75, balance, 0.000001)
+}
--- a/backend/internal/repository/usage_log_repo.go
+++ b/backend/internal/repository/usage_log_repo.go
--- a/backend/internal/repository/usage_log_repo_integration_test.go
+++ b/backend/internal/repository/usage_log_repo_integration_test.go
@@ -4,6 +4,8 @@ package repository

 import (
 	"context"
+	"fmt"
+	"sync"
 	"testing"
 	"time"

@@ -14,6 +16,7 @@ import (
 	"github.com/Wei-Shaw/sub2api/internal/pkg/timezone"
 	"github.com/Wei-Shaw/sub2api/internal/pkg/usagestats"
 	"github.com/Wei-Shaw/sub2api/internal/service"
+	"github.com/stretchr/testify/require"
 	"github.com/stretchr/testify/suite"
 )

@@ -84,6 +87,367 @@ func (s *UsageLogRepoSuite) TestCreate() {
 	s.Require().NotZero(log.ID)
 }

+func TestUsageLogRepositoryCreate_BatchPathConcurrent(t *testing.T) {
+	ctx := context.Background()
+	client := testEntClient(t)
+	repo := newUsageLogRepositoryWithSQL(client, integrationDB)
+
+	user := mustCreateUser(t, client, &service.User{Email: fmt.Sprintf("usage-batch-%d@example.com", time.Now().UnixNano())})
+	apiKey := mustCreateApiKey(t, client, &service.APIKey{UserID: user.ID, Key: "sk-usage-batch-" + uuid.NewString(), Name: "k"})
+	account := mustCreateAccount(t, client, &service.Account{Name: "acc-usage-batch-" + uuid.NewString()})
+
+	const total = 16
+	results := make([]bool, total)
+	errs := make([]error, total)
+	logs := make([]*service.UsageLog, total)
+
+	var wg sync.WaitGroup
+	wg.Add(total)
+	for i := 0; i < total; i++ {
+		i := i
+		logs[i] = &service.UsageLog{
+			UserID:       user.ID,
+			APIKeyID:     apiKey.ID,
+			AccountID:    account.ID,
+			RequestID:    uuid.NewString(),
+			Model:        "claude-3",
+			InputTokens:  10 + i,
+			OutputTokens: 20 + i,
+			TotalCost:    0.5,
+			ActualCost:   0.5,
+			CreatedAt:    time.Now().UTC(),
+		}
+		go func() {
+			defer wg.Done()
+			results[i], errs[i] = repo.Create(ctx, logs[i])
+		}()
+	}
+	wg.Wait()
+
+	for i := 0; i < total; i++ {
+		require.NoError(t, errs[i])
+		require.True(t, results[i])
+		require.NotZero(t, logs[i].ID)
+	}
+
+	var count int
+	require.NoError(t, integrationDB.QueryRowContext(ctx, "SELECT COUNT(*) FROM usage_logs WHERE api_key_id = $1", apiKey.ID).Scan(&count))
+	require.Equal(t, total, count)
+}
+
+func TestUsageLogRepositoryCreate_BatchPathDuplicateRequestID(t *testing.T) {
+	ctx := context.Background()
+	client := testEntClient(t)
+	repo := newUsageLogRepositoryWithSQL(client, integrationDB)
+
+	user := mustCreateUser(t, client, &service.User{Email: fmt.Sprintf("usage-dup-%d@example.com", time.Now().UnixNano())})
+	apiKey := mustCreateApiKey(t, client, &service.APIKey{UserID: user.ID, Key: "sk-usage-dup-" + uuid.NewString(), Name: "k"})
+	account := mustCreateAccount(t, client, &service.Account{Name: "acc-usage-dup-" + uuid.NewString()})
+	requestID := uuid.NewString()
+
+	log1 := &service.UsageLog{
+		UserID:       user.ID,
+		APIKeyID:     apiKey.ID,
+		AccountID:    account.ID,
+		RequestID:    requestID,
+		Model:        "claude-3",
+		InputTokens:  10,
+		OutputTokens: 20,
+		TotalCost:    0.5,
+		ActualCost:   0.5,
+		CreatedAt:    time.Now().UTC(),
+	}
+	log2 := &service.UsageLog{
+		UserID:       user.ID,
+		APIKeyID:     apiKey.ID,
+		AccountID:    account.ID,
+		RequestID:    requestID,
+		Model:        "claude-3",
+		InputTokens:  10,
+		OutputTokens: 20,
+		TotalCost:    0.5,
+		ActualCost:   0.5,
+		CreatedAt:    time.Now().UTC(),
+	}
+
+	inserted1, err1 := repo.Create(ctx, log1)
+	inserted2, err2 := repo.Create(ctx, log2)
+	require.NoError(t, err1)
+	require.NoError(t, err2)
+	require.True(t, inserted1)
+	require.False(t, inserted2)
+	require.Equal(t, log1.ID, log2.ID)
+
+	var count int
+	require.NoError(t, integrationDB.QueryRowContext(ctx, "SELECT COUNT(*) FROM usage_logs WHERE request_id = $1 AND api_key_id = $2", requestID, apiKey.ID).Scan(&count))
+	require.Equal(t, 1, count)
+}
+
+func TestUsageLogRepositoryFlushCreateBatch_DeduplicatesSameKeyInMemory(t *testing.T) {
+	ctx := context.Background()
+	client := testEntClient(t)
+	repo := newUsageLogRepositoryWithSQL(client, integrationDB)
+
+	user := mustCreateUser(t, client, &service.User{Email: fmt.Sprintf("usage-batch-memdup-%d@example.com", time.Now().UnixNano())})
+	apiKey := mustCreateApiKey(t, client, &service.APIKey{UserID: user.ID, Key: "sk-usage-batch-memdup-" + uuid.NewString(), Name: "k"})
+	account := mustCreateAccount(t, client, &service.Account{Name: "acc-usage-batch-memdup-" + uuid.NewString()})
+	requestID := uuid.NewString()
+
+	const total = 8
+	batch := make([]usageLogCreateRequest, 0, total)
+	logs := make([]*service.UsageLog, 0, total)
+
+	for i := 0; i < total; i++ {
+		log := &service.UsageLog{
+			UserID:       user.ID,
+			APIKeyID:     apiKey.ID,
+			AccountID:    account.ID,
+			RequestID:    requestID,
+			Model:        "claude-3",
+			InputTokens:  10 + i,
+			OutputTokens: 20 + i,
+			TotalCost:    0.5,
+			ActualCost:   0.5,
+			CreatedAt:    time.Now().UTC(),
+		}
+		logs = append(logs, log)
+		batch = append(batch, usageLogCreateRequest{
+			log:      log,
+			prepared: prepareUsageLogInsert(log),
+			resultCh: make(chan usageLogCreateResult, 1),
+		})
+	}
+
+	repo.flushCreateBatch(integrationDB, batch)
+
+	insertedCount := 0
+	var firstID int64
+	for idx, req := range batch {
+		res := <-req.resultCh
+		require.NoError(t, res.err)
+		if res.inserted {
+			insertedCount++
+		}
+		require.NotZero(t, logs[idx].ID)
+		if idx == 0 {
+			firstID = logs[idx].ID
+		} else {
+			require.Equal(t, firstID, logs[idx].ID)
+		}
+	}
+
+	require.Equal(t, 1, insertedCount)
+
+	var count int
+	require.NoError(t, integrationDB.QueryRowContext(ctx, "SELECT COUNT(*) FROM usage_logs WHERE request_id = $1 AND api_key_id = $2", requestID, apiKey.ID).Scan(&count))
+	require.Equal(t, 1, count)
+}
+
+func TestUsageLogRepositoryCreateBestEffort_BatchPathDuplicateRequestID(t *testing.T) {
+	ctx := context.Background()
+	client := testEntClient(t)
+	repo := newUsageLogRepositoryWithSQL(client, integrationDB)
+
+	user := mustCreateUser(t, client, &service.User{Email: fmt.Sprintf("usage-best-effort-dup-%d@example.com", time.Now().UnixNano())})
+	apiKey := mustCreateApiKey(t, client, &service.APIKey{UserID: user.ID, Key: "sk-usage-best-effort-dup-" + uuid.NewString(), Name: "k"})
+	account := mustCreateAccount(t, client, &service.Account{Name: "acc-usage-best-effort-dup-" + uuid.NewString()})
+	requestID := uuid.NewString()
+
+	log1 := &service.UsageLog{
+		UserID:       user.ID,
+		APIKeyID:     apiKey.ID,
+		AccountID:    account.ID,
+		RequestID:    requestID,
+		Model:        "claude-3",
+		InputTokens:  10,
+		OutputTokens: 20,
+		TotalCost:    0.5,
+		ActualCost:   0.5,
+		CreatedAt:    time.Now().UTC(),
+	}
+	log2 := &service.UsageLog{
+		UserID:       user.ID,
+		APIKeyID:     apiKey.ID,
+		AccountID:    account.ID,
+		RequestID:    requestID,
+		Model:        "claude-3",
+		InputTokens:  10,
+		OutputTokens: 20,
+		TotalCost:    0.5,
+		ActualCost:   0.5,
+		CreatedAt:    time.Now().UTC(),
+	}
+
+	require.NoError(t, repo.CreateBestEffort(ctx, log1))
+	require.NoError(t, repo.CreateBestEffort(ctx, log2))
+
+	require.Eventually(t, func() bool {
+		var count int
+		err := integrationDB.QueryRowContext(ctx, "SELECT COUNT(*) FROM usage_logs WHERE request_id = $1 AND api_key_id = $2", requestID, apiKey.ID).Scan(&count)
+		return err == nil && count == 1
+	}, 3*time.Second, 20*time.Millisecond)
+}
+
+func TestUsageLogRepositoryCreateBestEffort_QueueFullReturnsDropped(t *testing.T) {
+	ctx := context.Background()
+	client := testEntClient(t)
+	repo := newUsageLogRepositoryWithSQL(client, integrationDB)
+	repo.bestEffortBatchCh = make(chan usageLogBestEffortRequest, 1)
+	repo.bestEffortBatchCh <- usageLogBestEffortRequest{}
+
+	user := mustCreateUser(t, client, &service.User{Email: fmt.Sprintf("usage-best-effort-full-%d@example.com", time.Now().UnixNano())})
+	apiKey := mustCreateApiKey(t, client, &service.APIKey{UserID: user.ID, Key: "sk-usage-best-effort-full-" + uuid.NewString(), Name: "k"})
+	account := mustCreateAccount(t, client, &service.Account{Name: "acc-usage-best-effort-full-" + uuid.NewString()})
+
+	err := repo.CreateBestEffort(ctx, &service.UsageLog{
+		UserID:       user.ID,
+		APIKeyID:     apiKey.ID,
+		AccountID:    account.ID,
+		RequestID:    uuid.NewString(),
+		Model:        "claude-3",
+		InputTokens:  10,
+		OutputTokens: 20,
+		TotalCost:    0.5,
+		ActualCost:   0.5,
+		CreatedAt:    time.Now().UTC(),
+	})
+
+	require.Error(t, err)
+	require.True(t, service.IsUsageLogCreateDropped(err))
+}
+
+func TestUsageLogRepositoryCreate_BatchPathCanceledContextMarksNotPersisted(t *testing.T) {
+	client := testEntClient(t)
+	repo := newUsageLogRepositoryWithSQL(client, integrationDB)
+
+	user := mustCreateUser(t, client, &service.User{Email: fmt.Sprintf("usage-cancel-%d@example.com", time.Now().UnixNano())})
+	apiKey := mustCreateApiKey(t, client, &service.APIKey{UserID: user.ID, Key: "sk-usage-cancel-" + uuid.NewString(), Name: "k"})
+	account := mustCreateAccount(t, client, &service.Account{Name: "acc-usage-cancel-" + uuid.NewString()})
+
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel()
+
+	inserted, err := repo.Create(ctx, &service.UsageLog{
+		UserID:       user.ID,
+		APIKeyID:     apiKey.ID,
+		AccountID:    account.ID,
+		RequestID:    uuid.NewString(),
+		Model:        "claude-3",
+		InputTokens:  10,
+		OutputTokens: 20,
+		TotalCost:    0.5,
+		ActualCost:   0.5,
+		CreatedAt:    time.Now().UTC(),
+	})
+
+	require.False(t, inserted)
+	require.Error(t, err)
+	require.True(t, service.IsUsageLogCreateNotPersisted(err))
+}
+
+func TestUsageLogRepositoryCreate_BatchPathQueueFullMarksNotPersisted(t *testing.T) {
+	ctx := context.Background()
+	client := testEntClient(t)
+	repo := newUsageLogRepositoryWithSQL(client, integrationDB)
+	repo.createBatchCh = make(chan usageLogCreateRequest, 1)
+	repo.createBatchCh <- usageLogCreateRequest{}
+
+	user := mustCreateUser(t, client, &service.User{Email: fmt.Sprintf("usage-create-full-%d@example.com", time.Now().UnixNano())})
+	apiKey := mustCreateApiKey(t, client, &service.APIKey{UserID: user.ID, Key: "sk-usage-create-full-" + uuid.NewString(), Name: "k"})
+	account := mustCreateAccount(t, client, &service.Account{Name: "acc-usage-create-full-" + uuid.NewString()})
+
+	inserted, err := repo.Create(ctx, &service.UsageLog{
+		UserID:       user.ID,
+		APIKeyID:     apiKey.ID,
+		AccountID:    account.ID,
+		RequestID:    uuid.NewString(),
+		Model:        "claude-3",
+		InputTokens:  10,
+		OutputTokens: 20,
+		TotalCost:    0.5,
+		ActualCost:   0.5,
+		CreatedAt:    time.Now().UTC(),
+	})
+
+	require.False(t, inserted)
+	require.Error(t, err)
+	require.True(t, service.IsUsageLogCreateNotPersisted(err))
+}
+
+func TestUsageLogRepositoryCreate_BatchPathCanceledAfterQueueMarksNotPersisted(t *testing.T) {
+	client := testEntClient(t)
+	repo := newUsageLogRepositoryWithSQL(client, integrationDB)
+	repo.createBatchCh = make(chan usageLogCreateRequest, 1)
+
+	user := mustCreateUser(t, client, &service.User{Email: fmt.Sprintf("usage-cancel-queued-%d@example.com", time.Now().UnixNano())})
+	apiKey := mustCreateApiKey(t, client, &service.APIKey{UserID: user.ID, Key: "sk-usage-cancel-queued-" + uuid.NewString(), Name: "k"})
+	account := mustCreateAccount(t, client, &service.Account{Name: "acc-usage-cancel-queued-" + uuid.NewString()})
+
+	ctx, cancel := context.WithCancel(context.Background())
+	errCh := make(chan error, 1)
+
+	go func() {
+		_, err := repo.createBatched(ctx, &service.UsageLog{
+			UserID:       user.ID,
+			APIKeyID:     apiKey.ID,
+			AccountID:    account.ID,
+			RequestID:    uuid.NewString(),
+			Model:        "claude-3",
+			InputTokens:  10,
+			OutputTokens: 20,
+			TotalCost:    0.5,
+			ActualCost:   0.5,
+			CreatedAt:    time.Now().UTC(),
+		})
+		errCh <- err
+	}()
+
+	req := <-repo.createBatchCh
+	require.NotNil(t, req.shared)
+	cancel()
+
+	err := <-errCh
+	require.Error(t, err)
+	require.True(t, service.IsUsageLogCreateNotPersisted(err))
+	completeUsageLogCreateRequest(req, usageLogCreateResult{inserted: false, err: service.MarkUsageLogCreateNotPersisted(context.Canceled)})
+}
+
+func TestUsageLogRepositoryFlushCreateBatch_CanceledRequestReturnsNotPersisted(t *testing.T) {
+	client := testEntClient(t)
+	repo := newUsageLogRepositoryWithSQL(client, integrationDB)
+
+	user := mustCreateUser(t, client, &service.User{Email: fmt.Sprintf("usage-flush-cancel-%d@example.com", time.Now().UnixNano())})
+	apiKey := mustCreateApiKey(t, client, &service.APIKey{UserID: user.ID, Key: "sk-usage-flush-cancel-" + uuid.NewString(), Name: "k"})
+	account := mustCreateAccount(t, client, &service.Account{Name: "acc-usage-flush-cancel-" + uuid.NewString()})
+
+	log := &service.UsageLog{
+		UserID:       user.ID,
+		APIKeyID:     apiKey.ID,
+		AccountID:    account.ID,
+		RequestID:    uuid.NewString(),
+		Model:        "claude-3",
+		InputTokens:  10,
+		OutputTokens: 20,
+		TotalCost:    0.5,
+		ActualCost:   0.5,
+		CreatedAt:    time.Now().UTC(),
+	}
+	req := usageLogCreateRequest{
+		log:      log,
+		prepared: prepareUsageLogInsert(log),
+		shared:   &usageLogCreateShared{},
+		resultCh: make(chan usageLogCreateResult, 1),
+	}
+	req.shared.state.Store(usageLogCreateStateCanceled)
+
+	repo.flushCreateBatch(integrationDB, []usageLogCreateRequest{req})
+
+	res := <-req.resultCh
+	require.False(t, res.inserted)
+	require.Error(t, res.err)
+	require.True(t, service.IsUsageLogCreateNotPersisted(res.err))
+}
+
 func (s *UsageLogRepoSuite) TestGetByID() {
 	user := mustCreateUser(s.T(), s.client, &service.User{Email: "getbyid@test.com"})
 	apiKey := mustCreateApiKey(s.T(), s.client, &service.APIKey{UserID: user.ID, Key: "sk-getbyid", Name: "k"})
--- a/backend/internal/repository/usage_log_repo_unit_test.go
+++ b/backend/internal/repository/usage_log_repo_unit_test.go
@@ -3,8 +3,11 @@
 package repository

 import (
+	"strings"
 	"testing"
+	"time"

+	"github.com/Wei-Shaw/sub2api/internal/service"
 	"github.com/stretchr/testify/require"
 )

@@ -39,3 +42,26 @@ func TestSafeDateFormat(t *testing.T) {
 		})
 	}
 }
+
+func TestBuildUsageLogBatchInsertQuery_UsesConflictDoNothing(t *testing.T) {
+	log := &service.UsageLog{
+		UserID:       1,
+		APIKeyID:     2,
+		AccountID:    3,
+		RequestID:    "req-batch-no-update",
+		Model:        "gpt-5",
+		InputTokens:  10,
+		OutputTokens: 5,
+		TotalCost:    1.2,
+		ActualCost:   1.2,
+		CreatedAt:    time.Now().UTC(),
+	}
+	prepared := prepareUsageLogInsert(log)
+
+	query, _ := buildUsageLogBatchInsertQuery([]string{usageLogBatchKey(log.RequestID, log.APIKeyID)}, map[string]usageLogInsertPrepared{
+		usageLogBatchKey(log.RequestID, log.APIKeyID): prepared,
+	})
+
+	require.Contains(t, query, "ON CONFLICT (request_id, api_key_id) DO NOTHING")
+	require.NotContains(t, strings.ToUpper(query), "DO UPDATE")
+}
--- a/backend/internal/repository/wire.go
+++ b/backend/internal/repository/wire.go
@@ -62,6 +62,7 @@ var ProviderSet = wire.NewSet(
 	NewAnnouncementRepository,
 	NewAnnouncementReadRepository,
 	NewUsageLogRepository,
+	NewUsageBillingRepository,
 	NewIdempotencyRepository,
 	NewUsageCleanupRepository,
 	NewDashboardAggregationRepository,