Embed timezone data in runtime binary

Reviewed-on: #3

README.md

@@ -59,9 +59,12 @@ Supported environment variables:
 - `MQTT_SCRUBBER_APP_FLUSH_TIMEOUT`
 - `MQTT_SCRUBBER_APP_LOG_LEVEL`
 - `MQTT_SCRUBBER_APP_HEALTH_ADDRESS`
+- `MQTT_SCRUBBER_APP_TASMOTA_TIME_ZONE`
 
 `MQTT_SCRUBBER_MQTT_TOPICS` expects a comma-separated list.
 
+Timezone-less Tasmota `Time` values are interpreted in `tasmota_time_zone`. Set it to your device timezone such as `Europe/Prague` so the stored timestamp matches the device-local clock. The default is `UTC` for deterministic behavior.
+
 You can also define optional per-device aliases in config with a top-level `device_aliases` object. Keys are normalized like device tags, so `kitchen-plug`, `Kitchen Plug`, and `kitchen_plug` all resolve to `kitchen_plug`.
 
 ## Run

cmd/mqqt-scrubber/main.go

@@ -8,6 +8,7 @@ import (
 	"os/signal"
 	"syscall"
 	"time"
+	_ "time/tzdata"
 
 	"mqqt-scrubber/internal/config"
 	"mqqt-scrubber/internal/health"

config.example.json

@@ -26,6 +26,7 @@
     "flush_interval": "10s",
     "flush_timeout": "10s",
     "log_level": "info",
-    "health_address": ":8080"
+	    "health_address": ":8080",
+	    "tasmota_time_zone": "Europe/Prague"
   }
 }

docker-compose.yml

@@ -8,6 +8,7 @@ services:
       - ./config.json:/app/config.json:ro
     environment:
       MQTT_SCRUBBER_APP_HEALTH_ADDRESS: ":8080"
+      MQTT_SCRUBBER_APP_TASMOTA_TIME_ZONE: "Europe/Prague"
     networks:
       - iot-network
     healthcheck:

docs/ARCHITECTURE.md

@@ -140,7 +140,7 @@ timestamp: payload Time or message receive time
 
 - prefer payload `Time` when present
 - accept RFC3339 and timezone-less Tasmota timestamps in the form `2006-01-02T15:04:05`
-- current implementation interprets timezone-less timestamps as UTC
+- interpret timezone-less timestamps in the configured `tasmota_time_zone` location and convert them to UTC for storage
 
 ## Failure handling
 

docs/grafana/tasmota-device-summary-dashboard.json

@@ -15,7 +15,7 @@
       }
     ]
   },
-  "description": "Fleet overview of known Tasmota devices with drilldown links into a dedicated per-device dashboard.",
+  "description": "Fleet overview of Tasmota devices using the latest derived per-device snapshot, with drilldown links into a dedicated per-device dashboard.",
   "editable": true,
   "fiscalYearStartMonth": 0,
   "graphTooltip": 0,
@@ -89,13 +89,13 @@
           },
           "editorMode": "code",
           "format": "table",
-          "query": "SELECT count(DISTINCT device) AS total_devices FROM (SELECT device FROM tasmota_state WHERE $__timeFilter(time) UNION ALL SELECT device FROM tasmota_sensor WHERE $__timeFilter(time))",
+          "query": "SELECT count(*) AS total_devices FROM (SELECT s.device FROM tasmota_device_snapshot s INNER JOIN (SELECT device, max(time) AS time FROM tasmota_device_snapshot GROUP BY device) latest ON s.device = latest.device AND s.time = latest.time)",
           "rawQuery": true,
-          "rawSql": "SELECT count(DISTINCT device) AS total_devices FROM (SELECT device FROM tasmota_state WHERE $__timeFilter(time) UNION ALL SELECT device FROM tasmota_sensor WHERE $__timeFilter(time))",
+          "rawSql": "SELECT count(*) AS total_devices FROM (SELECT s.device FROM tasmota_device_snapshot s INNER JOIN (SELECT device, max(time) AS time FROM tasmota_device_snapshot GROUP BY device) latest ON s.device = latest.device AND s.time = latest.time)",
           "refId": "A"
         }
       ],
-      "title": "Total Devices",
+      "title": "Tracked Devices",
       "type": "stat"
     },
     {
@@ -152,13 +152,13 @@
           },
           "editorMode": "code",
           "format": "table",
-          "query": "SELECT count(DISTINCT device) AS power_devices FROM tasmota_sensor WHERE $__timeFilter(time) AND (energy_power IS NOT NULL OR energy_today IS NOT NULL OR energy_total IS NOT NULL)",
+          "query": "SELECT count(*) AS power_devices FROM (SELECT s.device FROM tasmota_device_snapshot s INNER JOIN (SELECT device, max(time) AS time FROM tasmota_device_snapshot GROUP BY device) latest ON s.device = latest.device AND s.time = latest.time WHERE s.energy_power IS NOT NULL OR s.energy_today IS NOT NULL OR s.energy_total IS NOT NULL)",
           "rawQuery": true,
-          "rawSql": "SELECT count(DISTINCT device) AS power_devices FROM tasmota_sensor WHERE $__timeFilter(time) AND (energy_power IS NOT NULL OR energy_today IS NOT NULL OR energy_total IS NOT NULL)",
+          "rawSql": "SELECT count(*) AS power_devices FROM (SELECT s.device FROM tasmota_device_snapshot s INNER JOIN (SELECT device, max(time) AS time FROM tasmota_device_snapshot GROUP BY device) latest ON s.device = latest.device AND s.time = latest.time WHERE s.energy_power IS NOT NULL OR s.energy_today IS NOT NULL OR s.energy_total IS NOT NULL)",
           "refId": "A"
         }
       ],
-      "title": "Devices With Energy Metrics",
+      "title": "Energy Devices",
       "type": "stat"
     },
     {
@@ -223,9 +223,9 @@
           },
           "editorMode": "code",
           "format": "table",
-          "query": "SELECT coalesce(sum(sensor.energy_power), 0) AS fleet_current_draw_w FROM (SELECT s.device, s.energy_power FROM tasmota_sensor s INNER JOIN (SELECT device, max(time) AS time FROM tasmota_sensor WHERE $__timeFilter(time) GROUP BY device) latest ON s.device = latest.device AND s.time = latest.time) sensor",
+          "query": "SELECT coalesce(sum(snapshots.energy_power), 0) AS fleet_current_draw_w FROM (SELECT s.device, s.energy_power FROM tasmota_device_snapshot s INNER JOIN (SELECT device, max(time) AS time FROM tasmota_device_snapshot GROUP BY device) latest ON s.device = latest.device AND s.time = latest.time) snapshots",
           "rawQuery": true,
-          "rawSql": "SELECT coalesce(sum(sensor.energy_power), 0) AS fleet_current_draw_w FROM (SELECT s.device, s.energy_power FROM tasmota_sensor s INNER JOIN (SELECT device, max(time) AS time FROM tasmota_sensor WHERE $__timeFilter(time) GROUP BY device) latest ON s.device = latest.device AND s.time = latest.time) sensor",
+          "rawSql": "SELECT coalesce(sum(snapshots.energy_power), 0) AS fleet_current_draw_w FROM (SELECT s.device, s.energy_power FROM tasmota_device_snapshot s INNER JOIN (SELECT device, max(time) AS time FROM tasmota_device_snapshot GROUP BY device) latest ON s.device = latest.device AND s.time = latest.time) snapshots",
           "refId": "A"
         }
       ],
@@ -286,9 +286,9 @@
           },
           "editorMode": "code",
           "format": "table",
-          "query": "SELECT coalesce(sum(sensor.energy_today), 0) AS fleet_daily_draw_kwh FROM (SELECT s.device, s.energy_today FROM tasmota_sensor s INNER JOIN (SELECT device, max(time) AS time FROM tasmota_sensor WHERE $__timeFilter(time) GROUP BY device) latest ON s.device = latest.device AND s.time = latest.time) sensor",
+          "query": "SELECT coalesce(sum(snapshots.energy_today), 0) AS fleet_daily_draw_kwh FROM (SELECT s.device, s.energy_today FROM tasmota_device_snapshot s INNER JOIN (SELECT device, max(time) AS time FROM tasmota_device_snapshot GROUP BY device) latest ON s.device = latest.device AND s.time = latest.time) snapshots",
           "rawQuery": true,
-          "rawSql": "SELECT coalesce(sum(sensor.energy_today), 0) AS fleet_daily_draw_kwh FROM (SELECT s.device, s.energy_today FROM tasmota_sensor s INNER JOIN (SELECT device, max(time) AS time FROM tasmota_sensor WHERE $__timeFilter(time) GROUP BY device) latest ON s.device = latest.device AND s.time = latest.time) sensor",
+          "rawSql": "SELECT coalesce(sum(snapshots.energy_today), 0) AS fleet_daily_draw_kwh FROM (SELECT s.device, s.energy_today FROM tasmota_device_snapshot s INNER JOIN (SELECT device, max(time) AS time FROM tasmota_device_snapshot GROUP BY device) latest ON s.device = latest.device AND s.time = latest.time) snapshots",
           "refId": "A"
         }
       ],
@@ -349,9 +349,9 @@
           },
           "editorMode": "code",
           "format": "table",
-          "query": "SELECT coalesce(sum(sensor.energy_total), 0) AS fleet_total_draw_kwh FROM (SELECT s.device, s.energy_total FROM tasmota_sensor s INNER JOIN (SELECT device, max(time) AS time FROM tasmota_sensor WHERE $__timeFilter(time) GROUP BY device) latest ON s.device = latest.device AND s.time = latest.time) sensor",
+          "query": "SELECT coalesce(sum(snapshots.energy_total), 0) AS fleet_total_draw_kwh FROM (SELECT s.device, s.energy_total FROM tasmota_device_snapshot s INNER JOIN (SELECT device, max(time) AS time FROM tasmota_device_snapshot GROUP BY device) latest ON s.device = latest.device AND s.time = latest.time) snapshots",
           "rawQuery": true,
-          "rawSql": "SELECT coalesce(sum(sensor.energy_total), 0) AS fleet_total_draw_kwh FROM (SELECT s.device, s.energy_total FROM tasmota_sensor s INNER JOIN (SELECT device, max(time) AS time FROM tasmota_sensor WHERE $__timeFilter(time) GROUP BY device) latest ON s.device = latest.device AND s.time = latest.time) sensor",
+          "rawSql": "SELECT coalesce(sum(snapshots.energy_total), 0) AS fleet_total_draw_kwh FROM (SELECT s.device, s.energy_total FROM tasmota_device_snapshot s INNER JOIN (SELECT device, max(time) AS time FROM tasmota_device_snapshot GROUP BY device) latest ON s.device = latest.device AND s.time = latest.time) snapshots",
           "refId": "A"
         }
       ],
@@ -579,9 +579,9 @@
           },
           "editorMode": "code",
           "format": "table",
-          "query": "SELECT devices.device, coalesce(meta.device_alias, state.device_alias, sensor.device_alias, '') AS alias, devices.last_seen, to_unixtime(now()) - to_unixtime(devices.last_seen) AS age_s, sensor.energy_power AS current_draw_w, sensor.energy_today AS daily_draw_kwh, sensor.energy_total AS total_draw_kwh, state.wifi_signal AS wifi_signal_dbm, state.uptime_sec / 3600.0 AS uptime_hours FROM (SELECT device, max(time) AS last_seen FROM (SELECT device, time FROM tasmota_state WHERE $__timeFilter(time) UNION ALL SELECT device, time FROM tasmota_sensor WHERE $__timeFilter(time)) all_messages GROUP BY device) devices LEFT JOIN (SELECT m.device, m.device_alias FROM tasmota_device_meta m INNER JOIN (SELECT device, max(time) AS time FROM tasmota_device_meta GROUP BY device) latest_meta ON m.device = latest_meta.device AND m.time = latest_meta.time) meta ON devices.device = meta.device LEFT JOIN (SELECT s.device, s.time, s.device_alias, s.energy_power, s.energy_today, s.energy_total FROM tasmota_sensor s INNER JOIN (SELECT device, max(time) AS time FROM tasmota_sensor WHERE $__timeFilter(time) GROUP BY device) latest_sensor ON s.device = latest_sensor.device AND s.time = latest_sensor.time) sensor ON devices.device = sensor.device LEFT JOIN (SELECT st.device, st.time, st.device_alias, st.wifi_signal, st.uptime_sec FROM tasmota_state st INNER JOIN (SELECT device, max(time) AS time FROM tasmota_state WHERE $__timeFilter(time) GROUP BY device) latest_state ON st.device = latest_state.device AND st.time = latest_state.time) state ON devices.device = state.device ORDER BY devices.device",
+          "query": "SELECT snapshots.device, coalesce(meta.device_alias, snapshots.device_alias, '') AS alias, snapshots.last_seen, to_unixtime(now()) - to_unixtime(snapshots.last_seen) AS age_s, snapshots.energy_power AS current_draw_w, snapshots.energy_today AS daily_draw_kwh, snapshots.energy_total AS total_draw_kwh, snapshots.wifi_signal AS wifi_signal_dbm, snapshots.uptime_sec / 3600.0 AS uptime_hours FROM (SELECT s.device, s.time AS last_seen, s.device_alias, s.energy_power, s.energy_today, s.energy_total, s.wifi_signal, s.uptime_sec FROM tasmota_device_snapshot s INNER JOIN (SELECT device, max(time) AS time FROM tasmota_device_snapshot GROUP BY device) latest ON s.device = latest.device AND s.time = latest.time) snapshots LEFT JOIN (SELECT m.device, m.device_alias FROM tasmota_device_meta m INNER JOIN (SELECT device, max(time) AS time FROM tasmota_device_meta GROUP BY device) latest_meta ON m.device = latest_meta.device AND m.time = latest_meta.time) meta ON snapshots.device = meta.device ORDER BY snapshots.device",
           "rawQuery": true,
-          "rawSql": "SELECT devices.device, coalesce(meta.device_alias, state.device_alias, sensor.device_alias, '') AS alias, devices.last_seen, to_unixtime(now()) - to_unixtime(devices.last_seen) AS age_s, sensor.energy_power AS current_draw_w, sensor.energy_today AS daily_draw_kwh, sensor.energy_total AS total_draw_kwh, state.wifi_signal AS wifi_signal_dbm, state.uptime_sec / 3600.0 AS uptime_hours FROM (SELECT device, max(time) AS last_seen FROM (SELECT device, time FROM tasmota_state WHERE $__timeFilter(time) UNION ALL SELECT device, time FROM tasmota_sensor WHERE $__timeFilter(time)) all_messages GROUP BY device) devices LEFT JOIN (SELECT m.device, m.device_alias FROM tasmota_device_meta m INNER JOIN (SELECT device, max(time) AS time FROM tasmota_device_meta GROUP BY device) latest_meta ON m.device = latest_meta.device AND m.time = latest_meta.time) meta ON devices.device = meta.device LEFT JOIN (SELECT s.device, s.time, s.device_alias, s.energy_power, s.energy_today, s.energy_total FROM tasmota_sensor s INNER JOIN (SELECT device, max(time) AS time FROM tasmota_sensor WHERE $__timeFilter(time) GROUP BY device) latest_sensor ON s.device = latest_sensor.device AND s.time = latest_sensor.time) sensor ON devices.device = sensor.device LEFT JOIN (SELECT st.device, st.time, st.device_alias, st.wifi_signal, st.uptime_sec FROM tasmota_state st INNER JOIN (SELECT device, max(time) AS time FROM tasmota_state WHERE $__timeFilter(time) GROUP BY device) latest_state ON st.device = latest_state.device AND st.time = latest_state.time) state ON devices.device = state.device ORDER BY devices.device",
+          "rawSql": "SELECT snapshots.device, coalesce(meta.device_alias, snapshots.device_alias, '') AS alias, snapshots.last_seen, to_unixtime(now()) - to_unixtime(snapshots.last_seen) AS age_s, snapshots.energy_power AS current_draw_w, snapshots.energy_today AS daily_draw_kwh, snapshots.energy_total AS total_draw_kwh, snapshots.wifi_signal AS wifi_signal_dbm, snapshots.uptime_sec / 3600.0 AS uptime_hours FROM (SELECT s.device, s.time AS last_seen, s.device_alias, s.energy_power, s.energy_today, s.energy_total, s.wifi_signal, s.uptime_sec FROM tasmota_device_snapshot s INNER JOIN (SELECT device, max(time) AS time FROM tasmota_device_snapshot GROUP BY device) latest ON s.device = latest.device AND s.time = latest.time) snapshots LEFT JOIN (SELECT m.device, m.device_alias FROM tasmota_device_meta m INNER JOIN (SELECT device, max(time) AS time FROM tasmota_device_meta GROUP BY device) latest_meta ON m.device = latest_meta.device AND m.time = latest_meta.time) meta ON snapshots.device = meta.device ORDER BY snapshots.device",
           "refId": "A"
         }
       ],
@@ -608,6 +608,6 @@
   "timezone": "browser",
   "title": "Tasmota Device Summary",
   "uid": "tasmota-device-summary",
-  "version": 8,
+  "version": 9,
   "weekStart": ""
 }

internal/config/config.go

@@ -39,12 +39,13 @@ type InfluxConfig struct {
 }
 
 type AppConfig struct {
-	BatchSize     int           `json:"batch_size"`
+	BatchSize       int           `json:"batch_size"`
-	BufferSize    int           `json:"buffer_size"`
+	BufferSize      int           `json:"buffer_size"`
-	FlushInterval DurationValue `json:"flush_interval"`
+	FlushInterval   DurationValue `json:"flush_interval"`
-	FlushTimeout  DurationValue `json:"flush_timeout"`
+	FlushTimeout    DurationValue `json:"flush_timeout"`
-	LogLevel      string        `json:"log_level"`
+	LogLevel        string        `json:"log_level"`
-	HealthAddress string        `json:"health_address"`
+	HealthAddress   string        `json:"health_address"`
+	TasmotaTimeZone string        `json:"tasmota_time_zone"`
 }
 
 type DurationValue struct {
@@ -124,6 +125,9 @@ func (cfg Config) Validate() error {
 	if cfg.App.FlushTimeout.Duration <= 0 {
 		return errors.New("app flush_timeout must be greater than zero")
 	}
+	if _, err := loadConfiguredLocation(cfg.App.TasmotaTimeZone); err != nil {
+		return err
+	}
 
 	return nil
 }
@@ -145,12 +149,13 @@ func defaultConfig() Config {
 			Precision: "ns",
 		},
 		App: AppConfig{
-			BatchSize:     200,
+			BatchSize:       200,
-			BufferSize:    1000,
+			BufferSize:      1000,
-			FlushInterval: DurationValue{Duration: 10 * time.Second},
+			FlushInterval:   DurationValue{Duration: 10 * time.Second},
-			FlushTimeout:  DurationValue{Duration: 10 * time.Second},
+			FlushTimeout:    DurationValue{Duration: 10 * time.Second},
-			LogLevel:      "info",
+			LogLevel:        "info",
-			HealthAddress: ":8080",
+			HealthAddress:   ":8080",
+			TasmotaTimeZone: "UTC",
 		},
 	}
 }
@@ -166,6 +171,7 @@ func applyEnvOverrides(cfg *Config) error {
 	setString(&cfg.Influx.Precision, envPrefix+"INFLUX_PRECISION")
 	setString(&cfg.App.LogLevel, envPrefix+"APP_LOG_LEVEL")
 	setString(&cfg.App.HealthAddress, envPrefix+"APP_HEALTH_ADDRESS")
+	setString(&cfg.App.TasmotaTimeZone, envPrefix+"APP_TASMOTA_TIME_ZONE")
 
 	if raw, ok := os.LookupEnv(envPrefix + "DEVICE_ALIASES"); ok {
 		if strings.TrimSpace(raw) == "" {
@@ -276,3 +282,29 @@ func normalizeDeviceKey(value string) string {
 	normalized = strings.Trim(normalized, "_")
 	return normalized
 }
+
+func (cfg AppConfig) TasmotaLocation() *time.Location {
+	location, err := loadConfiguredLocation(cfg.TasmotaTimeZone)
+	if err != nil {
+		return time.UTC
+	}
+
+	return location
+}
+
+func loadConfiguredLocation(name string) (*time.Location, error) {
+	trimmed := strings.TrimSpace(name)
+	if trimmed == "" || strings.EqualFold(trimmed, "utc") {
+		return time.UTC, nil
+	}
+	if strings.EqualFold(trimmed, "local") {
+		return time.Local, nil
+	}
+
+	location, err := time.LoadLocation(trimmed)
+	if err != nil {
+		return nil, fmt.Errorf("app tasmota_time_zone %q is invalid: %w", trimmed, err)
+	}
+
+	return location, nil
+}

internal/config/config_test.go

@@ -7,8 +7,6 @@ import (
 )
 
 func TestLoadNormalizesDeviceAliases(t *testing.T) {
-	t.Setenv("MQTT_SCRUBBER_DEVICE_ALIASES", "")
-
 	configPath := filepath.Join(t.TempDir(), "config.json")
 	contents := `{
 	  "mqtt": {
@@ -105,3 +103,76 @@ func TestLoadOverridesDeviceAliasesFromEnv(t *testing.T) {
 		t.Fatalf("unexpected desk alias: got %q", got)
 	}
 }
+
+func TestLoadSupportsTasmotaTimeZone(t *testing.T) {
+	configPath := filepath.Join(t.TempDir(), "config.json")
+	contents := `{
+	  "mqtt": {
+	    "broker": "tcp://127.0.0.1:1883",
+	    "client_id": "mqqt-scrubber",
+	    "topics": ["tele/+/STATE"],
+	    "qos": 0
+	  },
+	  "influx": {
+	    "url": "http://127.0.0.1:8181",
+	    "database": "home",
+	    "precision": "ns"
+	  },
+	  "app": {
+	    "batch_size": 200,
+	    "buffer_size": 1000,
+	    "flush_interval": "10s",
+	    "flush_timeout": "10s",
+	    "log_level": "info",
+	    "health_address": ":8080",
+	    "tasmota_time_zone": "Europe/Prague"
+	  }
+	}`
+
+	if err := os.WriteFile(configPath, []byte(contents), 0o644); err != nil {
+		t.Fatalf("write config file: %v", err)
+	}
+
+	cfg, err := Load(configPath)
+	if err != nil {
+		t.Fatalf("Load returned error: %v", err)
+	}
+
+	if got := cfg.App.TasmotaLocation().String(); got != "Europe/Prague" {
+		t.Fatalf("unexpected tasmota timezone: got %q", got)
+	}
+}
+
+func TestLoadRejectsInvalidTasmotaTimeZone(t *testing.T) {
+	configPath := filepath.Join(t.TempDir(), "config.json")
+	contents := `{
+	  "mqtt": {
+	    "broker": "tcp://127.0.0.1:1883",
+	    "client_id": "mqqt-scrubber",
+	    "topics": ["tele/+/STATE"],
+	    "qos": 0
+	  },
+	  "influx": {
+	    "url": "http://127.0.0.1:8181",
+	    "database": "home",
+	    "precision": "ns"
+	  },
+	  "app": {
+	    "batch_size": 200,
+	    "buffer_size": 1000,
+	    "flush_interval": "10s",
+	    "flush_timeout": "10s",
+	    "log_level": "info",
+	    "health_address": ":8080",
+	    "tasmota_time_zone": "Not/AZone"
+	  }
+	}`
+
+	if err := os.WriteFile(configPath, []byte(contents), 0o644); err != nil {
+		t.Fatalf("write config file: %v", err)
+	}
+
+	if _, err := Load(configPath); err == nil {
+		t.Fatal("expected Load to reject invalid tasmota_time_zone")
+	}
+}

internal/parser/tasmota.go

@@ -22,6 +22,14 @@ var tasmotaTimeLayouts = []string{
 }
 
 func ParseTasmota(message model.RawMessage) ([]model.Record, error) {
+	return ParseTasmotaInLocation(message, time.UTC)
+}
+
+func ParseTasmotaInLocation(message model.RawMessage, timezoneLessTimeLocation *time.Location) ([]model.Record, error) {
+	if timezoneLessTimeLocation == nil {
+		timezoneLessTimeLocation = time.UTC
+	}
+
 	parts := strings.Split(message.Topic, "/")
 	if len(parts) != 3 {
 		return nil, fmt.Errorf("unsupported topic shape: %s", message.Topic)
@@ -52,7 +60,7 @@ func ParseTasmota(message model.RawMessage) ([]model.Record, error) {
 		return nil, fmt.Errorf("no usable fields in payload for topic %s", message.Topic)
 	}
 
-	timestamp := parsePayloadTimestamp(payload, message.ReceivedAt)
+	timestamp := parsePayloadTimestamp(payload, message.ReceivedAt, timezoneLessTimeLocation)
 
 	record := model.Record{
 		Measurement: measurement,
@@ -77,11 +85,14 @@ func parseLWT(message model.RawMessage, measurement string, tags map[string]stri
 	}
 }
 
-func parsePayloadTimestamp(payload map[string]any, fallback time.Time) time.Time {
+func parsePayloadTimestamp(payload map[string]any, fallback time.Time, timezoneLessTimeLocation *time.Location) time.Time {
 	rawTime, ok := payload["Time"].(string)
 	if !ok || strings.TrimSpace(rawTime) == "" {
 		return fallback
 	}
+	if timezoneLessTimeLocation == nil {
+		timezoneLessTimeLocation = time.UTC
+	}
 
 	for _, layout := range tasmotaTimeLayouts {
 		var (
@@ -90,13 +101,13 @@ func parsePayloadTimestamp(payload map[string]any, fallback time.Time) time.Time
 		)
 
 		if layout == "2006-01-02T15:04:05" {
-			parsed, err = time.ParseInLocation(layout, rawTime, time.UTC)
+			parsed, err = time.ParseInLocation(layout, rawTime, timezoneLessTimeLocation)
 		} else {
 			parsed, err = time.Parse(layout, rawTime)
 		}
 
 		if err == nil {
-			return parsed
+			return parsed.UTC()
 		}
 	}
 

internal/parser/tasmota_test.go

@@ -85,6 +85,29 @@ func TestParseTasmotaFixtures(t *testing.T) {
 	}
 }
 
+func TestParseTasmotaInLocationUsesConfiguredTimezoneForTimezoneLessTime(t *testing.T) {
+	location := time.FixedZone("CET", 3600)
+	receivedAt := time.Date(2026, time.March, 16, 11, 55, 30, 0, time.UTC)
+
+	records, err := ParseTasmotaInLocation(model.RawMessage{
+		Topic:      "tele/tasmota_67850B/SENSOR",
+		Payload:    []byte(`{"Time":"2026-03-16T11:55:29","ENERGY":{"Power":9}}`),
+		ReceivedAt: receivedAt,
+	}, location)
+	if err != nil {
+		t.Fatalf("ParseTasmotaInLocation returned error: %v", err)
+	}
+
+	if len(records) != 1 {
+		t.Fatalf("expected 1 record, got %d", len(records))
+	}
+
+	want := time.Date(2026, time.March, 16, 10, 55, 29, 0, time.UTC)
+	if !records[0].Timestamp.Equal(want) {
+		t.Fatalf("unexpected timestamp: got %s want %s", records[0].Timestamp.Format(time.RFC3339), want.Format(time.RFC3339))
+	}
+}
+
 func fieldEquals(got any, want any) bool {
 	switch typedWant := want.(type) {
 	case float64:

internal/pipeline/service.go

@@ -21,16 +21,19 @@ type writer interface {
 }
 
 type Service struct {
-	config        config.Config
+	config              config.Config
-	deviceAliases map[string]string
+	tasmotaTimeLocation *time.Location
-	aliasRecords  []model.Record
+	deviceAliases       map[string]string
-	influxClient  writer
+	aliasRecords        []model.Record
-	input         chan model.RawMessage
+	snapshots           map[string]*deviceSnapshot
-	received      atomic.Uint64
+	dirtyDevices        map[string]struct{}
-	parsed        atomic.Uint64
+	influxClient        writer
-	written       atomic.Uint64
+	input               chan model.RawMessage
-	dropped       atomic.Uint64
+	received            atomic.Uint64
-	failed        atomic.Uint64
+	parsed              atomic.Uint64
+	written             atomic.Uint64
+	dropped             atomic.Uint64
+	failed              atomic.Uint64
 }
 
 type Snapshot struct {
@@ -41,14 +44,26 @@ type Snapshot struct {
 	Failed   uint64 `json:"failed"`
 }
 
+type deviceSnapshot struct {
+	Device     string
+	Alias      string
+	LastSeen   time.Time
+	StateSeen  time.Time
+	SensorSeen time.Time
+	Fields     map[string]any
+}
+
 func NewService(cfg config.Config, influxClient writer) *Service {
 	normalizedAliases := normalizeDeviceAliases(cfg.DeviceAliases)
 	return &Service{
-		config:        cfg,
+		config:              cfg,
-		deviceAliases: normalizedAliases,
+		tasmotaTimeLocation: cfg.App.TasmotaLocation(),
-		aliasRecords:  buildAliasRecords(normalizedAliases),
+		deviceAliases:       normalizedAliases,
-		influxClient:  influxClient,
+		aliasRecords:        buildAliasRecords(normalizedAliases),
-		input:         make(chan model.RawMessage, cfg.App.BufferSize),
+		snapshots:           make(map[string]*deviceSnapshot),
+		dirtyDevices:        make(map[string]struct{}),
+		influxClient:        influxClient,
+		input:               make(chan model.RawMessage, cfg.App.BufferSize),
 	}
 }
 
@@ -91,7 +106,7 @@ func (service *Service) Run(ctx context.Context) error {
 		select {
 		case <-ctx.Done():
 			flushCtx, cancel := context.WithTimeout(context.Background(), service.config.App.FlushTimeout.Duration)
-			err := service.flush(flushCtx, batch)
+			err := service.flushPending(flushCtx, batch)
 			cancel()
 			if err != nil {
 				return err
@@ -100,7 +115,7 @@ func (service *Service) Run(ctx context.Context) error {
 			service.logCounters()
 			return nil
 		case message := <-input:
-			records, err := parser.ParseTasmota(message)
+			records, err := parser.ParseTasmotaInLocation(message, service.tasmotaTimeLocation)
 			if err != nil {
 				service.failed.Add(1)
 				slog.Warn("failed to parse message", "topic", message.Topic, "error", err)
@@ -108,13 +123,14 @@ func (service *Service) Run(ctx context.Context) error {
 			}
 
 			service.applyDeviceAliases(records)
+			service.updateDeviceSnapshots(records)
 
 			service.parsed.Add(uint64(len(records)))
 			batch = append(batch, records...)
 
 			if len(batch) >= service.config.App.BatchSize {
 				flushCtx, cancel := context.WithTimeout(ctx, service.config.App.FlushTimeout.Duration)
-				err := service.flush(flushCtx, batch)
+				err := service.flushPending(flushCtx, batch)
 				cancel()
 				if err != nil {
 					slog.Error("failed to flush full batch to influx; keeping batch in memory", "count", len(batch), "error", err)
@@ -123,12 +139,12 @@ func (service *Service) Run(ctx context.Context) error {
 				batch = batch[:0]
 			}
 		case <-ticker.C:
-			if len(batch) == 0 {
+			if len(batch) == 0 && len(service.dirtyDevices) == 0 {
 				continue
 			}
 
 			flushCtx, cancel := context.WithTimeout(ctx, service.config.App.FlushTimeout.Duration)
-			err := service.flush(flushCtx, batch)
+			err := service.flushPending(flushCtx, batch)
 			cancel()
 			if err != nil {
 				slog.Error("failed to flush batch to influx; will retry on next interval", "count", len(batch), "error", err)
@@ -139,6 +155,18 @@ func (service *Service) Run(ctx context.Context) error {
 	}
 }
 
+func (service *Service) flushPending(ctx context.Context, batch []model.Record) error {
+	flushBatch := append([]model.Record(nil), batch...)
+	flushBatch = append(flushBatch, service.buildSnapshotRecords()...)
+
+	if err := service.flush(ctx, flushBatch); err != nil {
+		return err
+	}
+
+	service.clearDirtyDevices()
+	return nil
+}
+
 func (service *Service) flush(ctx context.Context, batch []model.Record) error {
 	if len(batch) == 0 {
 		return nil
@@ -189,6 +217,107 @@ func (service *Service) applyDeviceAliases(records []model.Record) {
 	}
 }
 
+func (service *Service) updateDeviceSnapshots(records []model.Record) {
+	for _, record := range records {
+		device := normalizeDeviceKey(record.Tags["device"])
+		if device == "" {
+			continue
+		}
+
+		snapshot, ok := service.snapshots[device]
+		if !ok {
+			snapshot = &deviceSnapshot{
+				Device: device,
+				Fields: make(map[string]any),
+			}
+			service.snapshots[device] = snapshot
+		}
+
+		if record.Timestamp.After(snapshot.LastSeen) {
+			snapshot.LastSeen = record.Timestamp
+		}
+
+		if alias, ok := record.Fields["device_alias"].(string); ok && strings.TrimSpace(alias) != "" {
+			snapshot.Alias = alias
+			snapshot.Fields["device_alias"] = alias
+		}
+
+		switch record.Tags["message_type"] {
+		case "state":
+			if record.Timestamp.After(snapshot.StateSeen) {
+				snapshot.StateSeen = record.Timestamp
+				copySnapshotFields(snapshot.Fields, record.Fields, "device_alias", "wifi_signal", "uptime_sec")
+			}
+		case "sensor":
+			if record.Timestamp.After(snapshot.SensorSeen) {
+				snapshot.SensorSeen = record.Timestamp
+				copySnapshotFields(snapshot.Fields, record.Fields, "device_alias", "energy_power", "energy_today", "energy_total")
+			}
+		}
+
+		service.dirtyDevices[device] = struct{}{}
+	}
+}
+
+func copySnapshotFields(target map[string]any, source map[string]any, keys ...string) {
+	for _, key := range keys {
+		value, ok := source[key]
+		if !ok {
+			continue
+		}
+		target[key] = value
+	}
+}
+
+func (service *Service) buildSnapshotRecords() []model.Record {
+	if len(service.dirtyDevices) == 0 {
+		return nil
+	}
+
+	devices := make([]string, 0, len(service.dirtyDevices))
+	for device := range service.dirtyDevices {
+		devices = append(devices, device)
+	}
+	sort.Strings(devices)
+
+	records := make([]model.Record, 0, len(devices))
+	for _, device := range devices {
+		snapshot := service.snapshots[device]
+		if snapshot == nil || snapshot.LastSeen.IsZero() {
+			continue
+		}
+
+		fields := make(map[string]any, len(snapshot.Fields)+2)
+		for key, value := range snapshot.Fields {
+			fields[key] = value
+		}
+		if !snapshot.StateSeen.IsZero() {
+			fields["state_last_seen_unix"] = snapshot.StateSeen.Unix()
+		}
+		if !snapshot.SensorSeen.IsZero() {
+			fields["sensor_last_seen_unix"] = snapshot.SensorSeen.Unix()
+		}
+
+		records = append(records, model.Record{
+			Measurement: "tasmota_device_snapshot",
+			Tags: map[string]string{
+				"device": device,
+				"source": "derived",
+			},
+			Fields:    fields,
+			Timestamp: snapshot.LastSeen,
+		})
+	}
+
+	return records
+}
+
+func (service *Service) clearDirtyDevices() {
+	for device := range service.dirtyDevices {
+		delete(service.dirtyDevices, device)
+	}
+}
+
 func normalizeDeviceAliases(aliases map[string]string) map[string]string {
 	if len(aliases) == 0 {
 		return nil

internal/pipeline/service_test.go

@@ -55,6 +55,17 @@ func (writer *fakeWriter) allBatches() [][]model.Record {
 	return copyBatches
 }
 
+func findRecord(records []model.Record, measurement string, device string) *model.Record {
+	for index := range records {
+		record := &records[index]
+		if record.Measurement == measurement && record.Tags["device"] == device {
+			return record
+		}
+	}
+
+	return nil
+}
+
 func TestServiceFlushesParsedRecords(t *testing.T) {
 	fake := newFakeWriter()
 	service := NewService(config.Config{
@@ -118,8 +129,8 @@ func TestServiceFlushesParsedRecords(t *testing.T) {
 	}
 
 	batch := batches[1]
-	if len(batch) != 2 {
+	if len(batch) != 4 {
-		t.Fatalf("expected 2 records in flushed batch, got %d", len(batch))
+		t.Fatalf("expected 4 records in flushed batch, got %d", len(batch))
 	}
 
 	if batch[0].Measurement != "tasmota_lwt" {
@@ -142,6 +153,34 @@ func TestServiceFlushesParsedRecords(t *testing.T) {
 		t.Fatalf("unexpected sensor device_alias field: %#v", batch[1].Fields["device_alias"])
 	}
 
+	garageSnapshot := findRecord(batch, "tasmota_device_snapshot", "tasmota_896001")
+	if garageSnapshot == nil {
+		t.Fatal("expected garage snapshot record in flushed batch")
+	}
+	if garageSnapshot.Fields["device_alias"] != "Garage Plug" {
+		t.Fatalf("unexpected garage snapshot alias: %#v", garageSnapshot.Fields["device_alias"])
+	}
+	if _, ok := garageSnapshot.Fields["sensor_last_seen_unix"]; ok {
+		t.Fatalf("did not expect sensor timestamp on lwt-only snapshot: %#v", garageSnapshot.Fields["sensor_last_seen_unix"])
+	}
+
+	officeSnapshot := findRecord(batch, "tasmota_device_snapshot", "tasmota_c88994")
+	if officeSnapshot == nil {
+		t.Fatal("expected office snapshot record in flushed batch")
+	}
+	if officeSnapshot.Fields["device_alias"] != "Office Plug" {
+		t.Fatalf("unexpected office snapshot alias: %#v", officeSnapshot.Fields["device_alias"])
+	}
+	if officeSnapshot.Fields["energy_total"] != float64(41.385) {
+		t.Fatalf("unexpected office snapshot energy_total: %#v", officeSnapshot.Fields["energy_total"])
+	}
+	if officeSnapshot.Fields["energy_power"] != float64(1) {
+		t.Fatalf("unexpected office snapshot energy_power: %#v", officeSnapshot.Fields["energy_power"])
+	}
+	if officeSnapshot.Fields["sensor_last_seen_unix"] != time.Date(2026, time.March, 12, 16, 23, 13, 0, time.UTC).Unix() {
+		t.Fatalf("unexpected office snapshot sensor timestamp: %#v", officeSnapshot.Fields["sensor_last_seen_unix"])
+	}
+
 	cancel()
 	select {
 	case err := <-errCh: