diff --git a/backend/internal/repository/ops_repo_latency_histogram_buckets.go b/backend/internal/repository/ops_repo_latency_histogram_buckets.go
index f7809480..cd5bed37 100644
--- a/backend/internal/repository/ops_repo_latency_histogram_buckets.go
+++ b/backend/internal/repository/ops_repo_latency_histogram_buckets.go
@@ -47,18 +47,18 @@ func latencyHistogramRangeCaseExpr(column string) string {
 
 func latencyHistogramRangeOrderCaseExpr(column string) string {
 	var sb strings.Builder
-	sb.WriteString("CASE\n")
+	_, _ = sb.WriteString("CASE\n")
 
 	order := 1
 	for _, b := range latencyHistogramBuckets {
 		if b.upperMs <= 0 {
 			continue
 		}
-		sb.WriteString(fmt.Sprintf("\tWHEN %s < %d THEN %d\n", column, b.upperMs, order))
+		_, _ = sb.WriteString(fmt.Sprintf("\tWHEN %s < %d THEN %d\n", column, b.upperMs, order))
 		order++
 	}
 
-	sb.WriteString(fmt.Sprintf("\tELSE %d\n", order))
-	sb.WriteString("END")
+	_, _ = sb.WriteString(fmt.Sprintf("\tELSE %d\n", order))
+	_, _ = sb.WriteString("END")
 	return sb.String()
 }
diff --git a/backend/internal/repository/ops_repo_request_details.go b/backend/internal/repository/ops_repo_request_details.go
index 678e1648..d8d5d111 100644
--- a/backend/internal/repository/ops_repo_request_details.go
+++ b/backend/internal/repository/ops_repo_request_details.go
@@ -187,7 +187,7 @@ LIMIT $%d OFFSET $%d
 	if err != nil {
 		return nil, 0, err
 	}
-	defer rows.Close()
+	defer func() { _ = rows.Close() }()
 
 	toIntPtr := func(v sql.NullInt64) *int {
 		if !v.Valid {
diff --git a/backend/internal/repository/ops_repo_trends.go b/backend/internal/repository/ops_repo_trends.go
index f25e157a..61b5ad64 100644
--- a/backend/internal/repository/ops_repo_trends.go
+++ b/backend/internal/repository/ops_repo_trends.go
@@ -77,7 +77,7 @@ ORDER BY bucket ASC`
 	if err != nil {
 		return nil, err
 	}
-	defer rows.Close()
+	defer func() { _ = rows.Close() }()
 
 	points := make([]*service.OpsThroughputTrendPoint, 0, 256)
 	for rows.Next() {
@@ -189,7 +189,7 @@ ORDER BY request_count DESC`
 	if err != nil {
 		return nil, err
 	}
-	defer rows.Close()
+	defer func() { _ = rows.Close() }()
 
 	items := make([]*service.OpsThroughputPlatformBreakdownItem, 0, 8)
 	for rows.Next() {
diff --git a/backend/internal/repository/usage_log_repo_integration_test.go b/backend/internal/repository/usage_log_repo_integration_test.go
index 51964782..591ee2f5 100644
--- a/backend/internal/repository/usage_log_repo_integration_test.go
+++ b/backend/internal/repository/usage_log_repo_integration_test.go
@@ -204,7 +204,7 @@ func (s *UsageLogRepoSuite) TestDashboardStats_TodayTotalsAndPerformance() {
 
 	userToday := mustCreateUser(s.T(), s.client, &service.User{
 		Email:     "today@example.com",
-		CreatedAt: maxTime(todayStart.Add(10*time.Second), now.Add(-10*time.Second)),
+		CreatedAt: testMaxTime(todayStart.Add(10*time.Second), now.Add(-10*time.Second)),
 		UpdatedAt: now,
 	})
 	userOld := mustCreateUser(s.T(), s.client, &service.User{
@@ -237,7 +237,7 @@ func (s *UsageLogRepoSuite) TestDashboardStats_TodayTotalsAndPerformance() {
 		TotalCost:           1.5,
 		ActualCost:          1.2,
 		DurationMs:          &d1,
-		CreatedAt:           maxTime(todayStart.Add(2*time.Minute), now.Add(-2*time.Minute)),
+		CreatedAt:           testMaxTime(todayStart.Add(2*time.Minute), now.Add(-2*time.Minute)),
 	}
 	_, err = s.repo.Create(s.ctx, logToday)
 	s.Require().NoError(err, "Create logToday")
@@ -621,7 +621,7 @@ func (s *UsageLogRepoSuite) TestGetGlobalStats() {
 	s.Require().Equal(int64(45), stats.TotalOutputTokens)
 }
 
-func maxTime(a, b time.Time) time.Time {
+func testMaxTime(a, b time.Time) time.Time {
 	if a.After(b) {
 		return a
 	}
diff --git a/backend/internal/service/ops_alert_models.go b/backend/internal/service/ops_alert_models.go
index 783a3d1e..0acf13ab 100644
--- a/backend/internal/service/ops_alert_models.go
+++ b/backend/internal/service/ops_alert_models.go
@@ -72,4 +72,3 @@ type OpsAlertEventFilter struct {
 	Platform string
 	GroupID  *int64
 }
-
diff --git a/backend/internal/service/ops_cleanup_service.go b/backend/internal/service/ops_cleanup_service.go
index c46ceaa9..afd2d22c 100644
--- a/backend/internal/service/ops_cleanup_service.go
+++ b/backend/internal/service/ops_cleanup_service.go
@@ -94,19 +94,19 @@ func (s *OpsCleanupService) Start() {
 			if parsed, err := time.LoadLocation(strings.TrimSpace(s.cfg.Timezone)); err == nil && parsed != nil {
 				loc = parsed
 			}
-			}
-	
-			c := cron.New(cron.WithParser(opsCleanupCronParser), cron.WithLocation(loc))
-			_, err := c.AddFunc(schedule, func() { s.runScheduled() })
-			if err != nil {
-				log.Printf("[OpsCleanup] not started (invalid schedule=%q): %v", schedule, err)
-				return
-			}
-			s.cron = c
-			s.cron.Start()
-			log.Printf("[OpsCleanup] started (schedule=%q tz=%s)", schedule, loc.String())
-		})
-	}
+		}
+
+		c := cron.New(cron.WithParser(opsCleanupCronParser), cron.WithLocation(loc))
+		_, err := c.AddFunc(schedule, func() { s.runScheduled() })
+		if err != nil {
+			log.Printf("[OpsCleanup] not started (invalid schedule=%q): %v", schedule, err)
+			return
+		}
+		s.cron = c
+		s.cron.Start()
+		log.Printf("[OpsCleanup] started (schedule=%q tz=%s)", schedule, loc.String())
+	})
+}
 
 func (s *OpsCleanupService) Stop() {
 	if s == nil {
diff --git a/backend/internal/service/ops_request_details.go b/backend/internal/service/ops_request_details.go
index e33e6f38..12b9aa1b 100644
--- a/backend/internal/service/ops_request_details.go
+++ b/backend/internal/service/ops_request_details.go
@@ -149,4 +149,3 @@ func (s *OpsService) ListRequestDetails(ctx context.Context, filter *OpsRequestD
 		PageSize: pageSize,
 	}, nil
 }
-
diff --git a/backend/internal/service/ops_retry.go b/backend/internal/service/ops_retry.go
index bf6213ae..747aa3b8 100644
--- a/backend/internal/service/ops_retry.go
+++ b/backend/internal/service/ops_retry.go
@@ -52,7 +52,6 @@ const (
 type limitedResponseWriter struct {
 	header      http.Header
 	wroteHeader bool
-	status      int
 
 	limit        int
 	totalWritten int64
@@ -65,7 +64,6 @@ func newLimitedResponseWriter(limit int) *limitedResponseWriter {
 	}
 	return &limitedResponseWriter{
 		header: make(http.Header),
-		status: http.StatusOK,
 		limit:  limit,
 	}
 }
@@ -79,7 +77,6 @@ func (w *limitedResponseWriter) WriteHeader(statusCode int) {
 		return
 	}
 	w.wroteHeader = true
-	w.status = statusCode
 }
 
 func (w *limitedResponseWriter) Write(p []byte) (int, error) {