perf(keys): bound latest IP lookup per key

backend/internal/repository/api_key_repo.go

@@ -524,17 +524,19 @@ func (r *apiKeyRepository) latestUsageLogIPs(ctx context.Context, apiKeyIDs []in
 
 func latestUsageLogIPsQuery(apiKeyIDs []int64, dialectName string) (string, []any) {
 	if dialectName == dialect.Postgres {
+		// Keep each key lookup bounded to one ordered index probe instead of ranking its full history.
 		return `
-		SELECT api_key_id, ip_address
-		FROM (
-			SELECT api_key_id, ip_address,
-				ROW_NUMBER() OVER (PARTITION BY api_key_id ORDER BY created_at DESC, id DESC) AS rn
-			FROM usage_logs
-			WHERE api_key_id = ANY($1::bigint[])
-				AND ip_address IS NOT NULL
-				AND ip_address <> ''
-		) ranked
-		WHERE rn = 1`, []any{pq.Array(apiKeyIDs)}
+		SELECT requested.api_key_id, latest.ip_address
+		FROM unnest($1::bigint[]) AS requested(api_key_id)
+		CROSS JOIN LATERAL (
+			SELECT ul.ip_address
+			FROM usage_logs AS ul
+			WHERE ul.api_key_id = requested.api_key_id
+				AND ul.ip_address IS NOT NULL
+				AND ul.ip_address <> ''
+			ORDER BY ul.created_at DESC, ul.id DESC
+			LIMIT 1
+		) AS latest`, []any{pq.Array(apiKeyIDs)}
 	}
 
 	placeholders := make([]string, len(apiKeyIDs))

backend/internal/repository/api_key_repo_last_used_unit_test.go

@@ -3,6 +3,7 @@ package repository
 import (
 	"context"
 	"database/sql"
+	"strings"
 	"testing"
 	"time"
 
@@ -125,6 +126,20 @@ func TestAPIKeyRepositoryListByUserIDAttachesLastUsedIP(t *testing.T) {
 	require.Nil(t, byID[noLogs.ID].LastUsedIP)
 }
 
+func TestLatestUsageLogIPsQueryPostgresUsesPerKeyLateralLookup(t *testing.T) {
+	query, args := latestUsageLogIPsQuery([]int64{11, 22}, dialect.Postgres)
+	normalizedQuery := strings.Join(strings.Fields(query), " ")
+
+	require.Contains(t, normalizedQuery, "FROM unnest($1::bigint[]) AS requested(api_key_id)")
+	require.Contains(t, normalizedQuery, "CROSS JOIN LATERAL")
+	require.Contains(t, normalizedQuery, "WHERE ul.api_key_id = requested.api_key_id")
+	require.Contains(t, normalizedQuery, "AND ul.ip_address IS NOT NULL")
+	require.Contains(t, normalizedQuery, "AND ul.ip_address <> ''")
+	require.Contains(t, normalizedQuery, "ORDER BY ul.created_at DESC, ul.id DESC LIMIT 1")
+	require.NotContains(t, normalizedQuery, "ROW_NUMBER")
+	require.Len(t, args, 1)
+}
+
 func TestAPIKeyRepository_CreateWithLastUsedAt(t *testing.T) {
 	repo, client := newAPIKeyRepoSQLite(t)
 	ctx := context.Background()