diff --git a/docs/ops/go-vehicle-ingest-memory.md b/docs/ops/go-vehicle-ingest-memory.md
index 82af8ca8..d46813e3 100644
--- a/docs/ops/go-vehicle-ingest-memory.md
+++ b/docs/ops/go-vehicle-ingest-memory.md
@@ -433,6 +433,15 @@ vehicle_fast_writer_stage_duration_ms_histogram_sum{subject,stage,status}
 
 2026-07-03 后续优化：`nats-fast-writer` 已从“Fetch batch 后逐条写 TDengine”改为“Fetch batch 后先调用 `history.Writer.AppendAllBatch` 批量写 TDengine，再逐条更新 Redis 和 ack”。这样可以减少 TDengine round trip；Redis/ack 仍按单条执行，避免某条实时投影失败时误 ack。
 
+2026-07-03 后续优化：`nats-fast-writer` 的 TDengine SQL 连接池已从固定 `1` 改为可配置：
+
+```text
+FAST_WRITER_TDENGINE_MAX_OPEN_CONNS
+FAST_WRITER_TDENGINE_MAX_IDLE_CONNS
+```
+
+默认 `max_open=1`、`max_idle=1`。原因是当前 TDengine 写入依赖启动时执行的 `USE <database>`；`database/sql` 连接池新建连接不会继承其他连接上的 `USE` 状态。实测默认跟随 worker 放大到 8 会导致 `[0x200] db is not specified` / `[0x2616] Database not specified`。后续只有在 TDengine DSN 或 writer SQL 改为每条连接都明确选库后，才能提高该连接池。
+
 同时新增 batch pending gauge：
 
 ```text
diff --git a/docs/ops/vehicle-ingest-runbook.md b/docs/ops/vehicle-ingest-runbook.md
index 7ba03b3b..94d617d1 100644
--- a/docs/ops/vehicle-ingest-runbook.md
+++ b/docs/ops/vehicle-ingest-runbook.md
@@ -136,7 +136,7 @@ go run ./cmd/load-sim \
 | `vehicle_fast_writer_nats_consumer_pending` | 持续增长且 `> 10000` | fast-writer 消费 NATS 的速度跟不上入口写入速度。 |
 | `vehicle_fast_writer_batch_pending_messages` | 持续非 0 或 burst 后不回落 | fast-writer 已拉取 NATS 消息但尚未完成 TDengine/Redis 写入和 ack。 |
 | `vehicle_fast_writer_batch_pending_envelopes` | 持续非 0 或 burst 后不回落 | fast-writer 当前批次已有有效 envelope 在等待落库或 ack。 |
-| `vehicle_fast_writer_stage_duration_ms_histogram_bucket` | 某个 stage 的 p99 连续 5 分钟上升 | NATS 快速写链路在 TDengine、Redis 或 NATS ack 某一阶段变慢。 |
+| `vehicle_fast_writer_stage_duration_ms_histogram_bucket` | 某个 stage 的 p99 连续 5 分钟上升 | NATS 快速写链路在 TDengine、Redis 或 NATS ack 某一阶段变慢；当前 TDengine 连接池默认保持 `1`，放大 `FAST_WRITER_TDENGINE_MAX_OPEN_CONNS` 前必须先确认每条连接都能明确选库。 |
 | `vehicle_realtime_store_update_duration_ms_histogram_bucket{store="redis"}` | p99 连续 5 分钟上升 | Redis 实时投影变慢，会直接影响 realtime consumer 追平能力。 |
 | `vehicle_realtime_store_update_duration_ms_histogram_bucket{store="mysql"}` | p99 连续 5 分钟上升 | MySQL 当前态/位置投影变慢，需结合 async queue depth 和 dropped 计数判断。 |
 | `vehicle_stat_write_duration_ms_histogram_bucket` | p99 连续 5 分钟上升 | MySQL 每日里程统计写入变慢，可能导致 stat Kafka lag 增长。 |
diff --git a/go/vehicle-gateway/cmd/nats-fast-writer/main.go b/go/vehicle-gateway/cmd/nats-fast-writer/main.go
index 7eb95da8..e7fc1013 100644
--- a/go/vehicle-gateway/cmd/nats-fast-writer/main.go
+++ b/go/vehicle-gateway/cmd/nats-fast-writer/main.go
@@ -66,8 +66,8 @@ func main() {
 		os.Exit(1)
 	}
 	defer tdDB.Close()
-	tdDB.SetMaxOpenConns(1)
-	tdDB.SetMaxIdleConns(1)
+	tdDB.SetMaxOpenConns(cfg.TDengineMaxOpenConns)
+	tdDB.SetMaxIdleConns(cfg.TDengineMaxIdleConns)
 	if err := tdDB.PingContext(ctx); err != nil {
 		logger.Error("tdengine ping failed", "error", err)
 		os.Exit(1)
@@ -117,6 +117,8 @@ func main() {
 		"filter", cfg.NATSFilter,
 		"batch_size", cfg.BatchSize,
 		"workers", cfg.Workers,
+		"tdengine_max_open_conns", cfg.TDengineMaxOpenConns,
+		"tdengine_max_idle_conns", cfg.TDengineMaxIdleConns,
 		"operation_timeout_ms", cfg.OperationWait.Milliseconds())
 	for i := 0; i < cfg.Workers; i++ {
 		go runFastWorker(ctx, logger, registry, js, sub, historyWriter, realtimeRepo, cfg)
@@ -141,6 +143,8 @@ type config struct {
 	TDengineDSN          string
 	TDengineDatabase     string
 	TDengineEnsureSchema bool
+	TDengineMaxOpenConns int
+	TDengineMaxIdleConns int
 	RedisAddr            string
 	RedisUsername        string
 	RedisPassword        string
@@ -157,6 +161,9 @@ func loadConfig() config {
 		env("NATS_SUBJECT_JT808_FIELDS", env("KAFKA_TOPIC_JT808_FIELDS", topics.FieldsJT808)),
 		env("NATS_SUBJECT_YUTONG_MQTT_FIELDS", env("KAFKA_TOPIC_YUTONG_MQTT_FIELDS", topics.FieldsYutongMQTT)),
 	}, ",")))
+	workers := envInt("FAST_WRITER_WORKERS", 8)
+	maxOpenConns := envInt("FAST_WRITER_TDENGINE_MAX_OPEN_CONNS", 1)
+	maxIdleConns := envInt("FAST_WRITER_TDENGINE_MAX_IDLE_CONNS", maxOpenConns)
 	return config{
 		NATSURL:              env("NATS_URL", "nats://127.0.0.1:4222"),
 		NATSClientName:       env("NATS_CLIENT_NAME", "lingniu-nats-fast-writer"),
@@ -169,11 +176,13 @@ func loadConfig() config {
 		OperationWait:        time.Duration(envInt("FAST_WRITER_OPERATION_TIMEOUT_MS", 100)) * time.Millisecond,
 		AckWait:              time.Duration(envInt("NATS_ACK_WAIT_SECONDS", 30)) * time.Second,
 		StreamMaxAge:         time.Duration(envInt("NATS_STREAM_MAX_AGE_HOURS", 24)) * time.Hour,
-		Workers:              envInt("FAST_WRITER_WORKERS", 8),
+		Workers:              workers,
 		TDengineDriver:       env("TDENGINE_DRIVER", "taosWS"),
 		TDengineDSN:          env("TDENGINE_DSN", ""),
 		TDengineDatabase:     env("TDENGINE_DATABASE", history.DefaultDatabase),
 		TDengineEnsureSchema: env("TDENGINE_ENSURE_SCHEMA", "true") != "false",
+		TDengineMaxOpenConns: maxOpenConns,
+		TDengineMaxIdleConns: maxIdleConns,
 		RedisAddr:            env("REDIS_ADDR", "127.0.0.1:6379"),
 		RedisUsername:        env("REDIS_USERNAME", ""),
 		RedisPassword:        env("REDIS_PASSWORD", ""),
diff --git a/go/vehicle-gateway/cmd/nats-fast-writer/main_test.go b/go/vehicle-gateway/cmd/nats-fast-writer/main_test.go
index 4052a9c5..2f67de67 100644
--- a/go/vehicle-gateway/cmd/nats-fast-writer/main_test.go
+++ b/go/vehicle-gateway/cmd/nats-fast-writer/main_test.go
@@ -197,6 +197,35 @@ func TestRecordFastNATSConsumerInfoMetrics(t *testing.T) {
 	}
 }
 
+func TestLoadConfigDefaultsTDenginePoolToSingleConnection(t *testing.T) {
+	t.Setenv("FAST_WRITER_WORKERS", "12")
+	t.Setenv("FAST_WRITER_TDENGINE_MAX_OPEN_CONNS", "")
+
+	cfg := loadConfig()
+
+	if cfg.TDengineMaxOpenConns != 1 {
+		t.Fatalf("TDengineMaxOpenConns = %d, want 1", cfg.TDengineMaxOpenConns)
+	}
+	if cfg.TDengineMaxIdleConns != 1 {
+		t.Fatalf("TDengineMaxIdleConns = %d, want 1", cfg.TDengineMaxIdleConns)
+	}
+}
+
+func TestLoadConfigReadsTDenginePoolOverride(t *testing.T) {
+	t.Setenv("FAST_WRITER_WORKERS", "12")
+	t.Setenv("FAST_WRITER_TDENGINE_MAX_OPEN_CONNS", "4")
+	t.Setenv("FAST_WRITER_TDENGINE_MAX_IDLE_CONNS", "2")
+
+	cfg := loadConfig()
+
+	if cfg.TDengineMaxOpenConns != 4 {
+		t.Fatalf("TDengineMaxOpenConns = %d, want 4", cfg.TDengineMaxOpenConns)
+	}
+	if cfg.TDengineMaxIdleConns != 2 {
+		t.Fatalf("TDengineMaxIdleConns = %d, want 2", cfg.TDengineMaxIdleConns)
+	}
+}
+
 type recordingFastAppender struct {
 	count         int
 	batchCount    int