perf(go): cache identity binding lookups

go/vehicle-gateway/internal/identity/resolver.go

@@ -26,12 +26,22 @@ type MySQLResolver struct {
 	db                    *sql.DB
 	table                 string
 	locationTouchInterval time.Duration
+	lookupCacheTTL        time.Duration
+	lookupMu              sync.Mutex
+	lookupCache           map[string]lookupCacheEntry
 	touchMu               sync.Mutex
 	locationTouches       map[string]time.Time
 }
 
 type MySQLResolverOptions struct {
 	LocationTouchInterval time.Duration
+	LookupCacheTTL        time.Duration
+}
+
+type lookupCacheEntry struct {
+	vin       string
+	notFound  bool
+	expiresAt time.Time
 }
 
 func NewMySQLResolver(db *sql.DB, table string) *MySQLResolver {
@@ -50,10 +60,16 @@ func NewMySQLResolverWithOptions(db *sql.DB, table string, opts MySQLResolverOpt
 	if interval <= 0 {
 		interval = 10 * time.Minute
 	}
+	lookupTTL := opts.LookupCacheTTL
+	if lookupTTL <= 0 {
+		lookupTTL = 10 * time.Minute
+	}
 	return &MySQLResolver{
 		db:                    db,
 		table:                 table,
 		locationTouchInterval: interval,
+		lookupCacheTTL:        lookupTTL,
+		lookupCache:           map[string]lookupCacheEntry{},
 		locationTouches:       map[string]time.Time{},
 	}
 }
@@ -161,9 +177,32 @@ func (r *MySQLResolver) Resolve(ctx context.Context, env envelope.FrameEnvelope)
 }
 
 func (r *MySQLResolver) lookup(ctx context.Context, column string, value string) (string, error) {
+	cacheKey := column + "\x00" + value
+	now := time.Now()
+	r.lookupMu.Lock()
+	cached, ok := r.lookupCache[cacheKey]
+	if ok && now.Before(cached.expiresAt) {
+		r.lookupMu.Unlock()
+		if cached.notFound {
+			return "", sql.ErrNoRows
+		}
+		return cached.vin, nil
+	}
+	r.lookupMu.Unlock()
+
 	query := "SELECT vin FROM " + r.table + " WHERE " + column + " = ? AND vin IS NOT NULL AND vin <> ''"
 	var vin string
 	err := r.db.QueryRowContext(ctx, query, value).Scan(&vin)
+	if err != nil && !errors.Is(err, sql.ErrNoRows) {
+		return "", err
+	}
+	r.lookupMu.Lock()
+	r.lookupCache[cacheKey] = lookupCacheEntry{
+		vin:       strings.TrimSpace(vin),
+		notFound:  errors.Is(err, sql.ErrNoRows),
+		expiresAt: now.Add(r.lookupCacheTTL),
+	}
+	r.lookupMu.Unlock()
 	return vin, err
 }