diff --git a/backend/database/__init__.py b/backend/database/__init__.py
index 2c5707d..f55a12e 100644
--- a/backend/database/__init__.py
+++ b/backend/database/__init__.py
@@ -1,7 +1,6 @@
-from database.core import (
+from database.pg_mqtt import (
     init_db,
     close_db,
-    get_db,
     purge_loop,
     purge_old_data,
     insert_log,
@@ -16,12 +15,13 @@ from database.core import (
     upsert_alert,
     delete_alert,
     get_alerts,
+    partition_manager_loop,
+    ensure_current_partitions,
 )
 
 __all__ = [
     "init_db",
     "close_db",
-    "get_db",
     "purge_loop",
     "purge_old_data",
     "insert_log",
@@ -36,4 +36,6 @@ __all__ = [
     "upsert_alert",
     "delete_alert",
     "get_alerts",
+    "partition_manager_loop",
+    "ensure_current_partitions",
 ]
diff --git a/backend/database/pg_mqtt.py b/backend/database/pg_mqtt.py
new file mode 100644
index 0000000..5534c4a
--- /dev/null
+++ b/backend/database/pg_mqtt.py
@@ -0,0 +1,416 @@
+"""
+Phase 5 — MQTT live data functions backed by Postgres.
+
+device_logs is a partitioned table; heartbeats and commands are plain tables.
+All three are accessed via raw SQL (not ORM) because device_logs partitioning
+does not play well with SQLAlchemy's declarative ORM.
+
+device_alerts is an ORM model (devices/orm.py) and is handled here via raw SQL
+to keep a single consistent interface for callers that used to import from database.core.
+"""
+
+import asyncio
+import json
+import logging
+from datetime import date, datetime, timedelta, timezone
+
+from dateutil.relativedelta import relativedelta
+from sqlalchemy import text
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from config import settings
+from database.postgres import AsyncSessionLocal
+
+logger = logging.getLogger("database.pg_mqtt")
+
+
+# ---------------------------------------------------------------------------
+# Internal session helper — used by fire-and-forget insert paths that are
+# called from the MQTT ingestion thread (not inside a FastAPI request).
+# ---------------------------------------------------------------------------
+
+async def _session() -> AsyncSession:
+    return AsyncSessionLocal()
+
+
+# ---------------------------------------------------------------------------
+# Insert operations
+# ---------------------------------------------------------------------------
+
+async def insert_log(device_serial: str, level: str, message: str,
+                     device_timestamp: int | None = None) -> int:
+    async with AsyncSessionLocal() as session:
+        result = await session.execute(
+            text("""
+                INSERT INTO device_logs (device_serial, level, message, device_timestamp, received_at)
+                VALUES (:serial, :level, :message, :ts, now())
+                RETURNING id
+            """),
+            {"serial": device_serial, "level": level, "message": message, "ts": device_timestamp},
+        )
+        row = result.fetchone()
+        await session.commit()
+        return row[0]
+
+
+async def insert_heartbeat(device_serial: str, device_id: str,
+                           firmware_version: str, ip_address: str,
+                           gateway: str, uptime_ms: int, uptime_display: str) -> int:
+    async with AsyncSessionLocal() as session:
+        result = await session.execute(
+            text("""
+                INSERT INTO heartbeats
+                    (device_serial, device_id, firmware_version, ip_address,
+                     gateway, uptime_ms, uptime_display, received_at)
+                VALUES
+                    (:serial, :device_id, :fw, :ip, :gw, :uptime_ms, :uptime_display, now())
+                RETURNING id
+            """),
+            {
+                "serial": device_serial,
+                "device_id": device_id,
+                "fw": firmware_version,
+                "ip": ip_address,
+                "gw": gateway,
+                "uptime_ms": uptime_ms,
+                "uptime_display": uptime_display,
+            },
+        )
+        row = result.fetchone()
+        await session.commit()
+        return row[0]
+
+
+async def insert_command(device_serial: str, command_name: str,
+                         command_payload: dict) -> int:
+    async with AsyncSessionLocal() as session:
+        result = await session.execute(
+            text("""
+                INSERT INTO commands (device_serial, command_name, command_payload, sent_at)
+                VALUES (:serial, :name, :payload, now())
+                RETURNING id
+            """),
+            {
+                "serial": device_serial,
+                "name": command_name,
+                "payload": json.dumps(command_payload),
+            },
+        )
+        row = result.fetchone()
+        await session.commit()
+        return row[0]
+
+
+async def update_command_response(command_id: int, status: str,
+                                  response_payload: dict | None = None):
+    async with AsyncSessionLocal() as session:
+        await session.execute(
+            text("""
+                UPDATE commands
+                SET status = :status,
+                    response_payload = :payload,
+                    responded_at = now()
+                WHERE id = :id
+            """),
+            {
+                "id": command_id,
+                "status": status,
+                "payload": json.dumps(response_payload) if response_payload else None,
+            },
+        )
+        await session.commit()
+
+
+# ---------------------------------------------------------------------------
+# Query operations
+# ---------------------------------------------------------------------------
+
+async def get_logs(device_serial: str, level: str | None = None,
+                   search: str | None = None,
+                   limit: int = 100, offset: int = 0) -> tuple[list, int]:
+    where = "device_serial = :serial"
+    params: dict = {"serial": device_serial, "limit": limit, "offset": offset}
+
+    if level:
+        where += " AND level = :level"
+        params["level"] = level
+    if search:
+        where += " AND message ILIKE :search"
+        params["search"] = f"%{search}%"
+
+    async with AsyncSessionLocal() as session:
+        count_result = await session.execute(
+            text(f"SELECT COUNT(*) FROM device_logs WHERE {where}"), params
+        )
+        total = count_result.scalar()
+
+        rows_result = await session.execute(
+            text(f"""
+                SELECT id, device_serial, level, message, device_timestamp,
+                       received_at AT TIME ZONE 'UTC' AS received_at
+                FROM device_logs
+                WHERE {where}
+                ORDER BY received_at DESC
+                LIMIT :limit OFFSET :offset
+            """),
+            params,
+        )
+        rows = rows_result.mappings().all()
+
+    return [_row_to_dict(r) for r in rows], total
+
+
+async def get_heartbeats(device_serial: str, limit: int = 100,
+                         offset: int = 0) -> tuple[list, int]:
+    async with AsyncSessionLocal() as session:
+        count_result = await session.execute(
+            text("SELECT COUNT(*) FROM heartbeats WHERE device_serial = :serial"),
+            {"serial": device_serial},
+        )
+        total = count_result.scalar()
+
+        rows_result = await session.execute(
+            text("""
+                SELECT id, device_serial, device_id, firmware_version, ip_address,
+                       gateway, uptime_ms, uptime_display,
+                       received_at AT TIME ZONE 'UTC' AS received_at
+                FROM heartbeats
+                WHERE device_serial = :serial
+                ORDER BY received_at DESC
+                LIMIT :limit OFFSET :offset
+            """),
+            {"serial": device_serial, "limit": limit, "offset": offset},
+        )
+        rows = rows_result.mappings().all()
+
+    return [_row_to_dict(r) for r in rows], total
+
+
+async def get_commands(device_serial: str, limit: int = 100,
+                       offset: int = 0) -> tuple[list, int]:
+    async with AsyncSessionLocal() as session:
+        count_result = await session.execute(
+            text("SELECT COUNT(*) FROM commands WHERE device_serial = :serial"),
+            {"serial": device_serial},
+        )
+        total = count_result.scalar()
+
+        rows_result = await session.execute(
+            text("""
+                SELECT id, device_serial, command_name, command_payload, status,
+                       response_payload,
+                       sent_at AT TIME ZONE 'UTC' AS sent_at,
+                       responded_at AT TIME ZONE 'UTC' AS responded_at
+                FROM commands
+                WHERE device_serial = :serial
+                ORDER BY sent_at DESC
+                LIMIT :limit OFFSET :offset
+            """),
+            {"serial": device_serial, "limit": limit, "offset": offset},
+        )
+        rows = rows_result.mappings().all()
+
+    return [_row_to_dict(r) for r in rows], total
+
+
+async def get_latest_heartbeats() -> list:
+    async with AsyncSessionLocal() as session:
+        rows_result = await session.execute(
+            text("""
+                SELECT DISTINCT ON (device_serial)
+                    id, device_serial, device_id, firmware_version, ip_address,
+                    gateway, uptime_ms, uptime_display,
+                    received_at AT TIME ZONE 'UTC' AS received_at
+                FROM heartbeats
+                ORDER BY device_serial, received_at DESC
+            """)
+        )
+        rows = rows_result.mappings().all()
+
+    return [_row_to_dict(r) for r in rows]
+
+
+async def get_pending_command(device_serial: str) -> dict | None:
+    async with AsyncSessionLocal() as session:
+        result = await session.execute(
+            text("""
+                SELECT id, device_serial, command_name, command_payload, status,
+                       response_payload,
+                       sent_at AT TIME ZONE 'UTC' AS sent_at,
+                       responded_at AT TIME ZONE 'UTC' AS responded_at
+                FROM commands
+                WHERE device_serial = :serial AND status = 'pending'
+                ORDER BY sent_at DESC
+                LIMIT 1
+            """),
+            {"serial": device_serial},
+        )
+        row = result.mappings().fetchone()
+
+    return _row_to_dict(row) if row else None
+
+
+# ---------------------------------------------------------------------------
+# Device alerts
+# ---------------------------------------------------------------------------
+
+async def upsert_alert(device_serial: str, subsystem: str, state: str,
+                       message: str | None = None):
+    async with AsyncSessionLocal() as session:
+        await session.execute(
+            text("""
+                INSERT INTO device_alerts (device_serial, subsystem, state, message, updated_at)
+                VALUES (:serial, :subsystem, :state, :message, now())
+                ON CONFLICT (device_serial, subsystem)
+                DO UPDATE SET
+                    state      = EXCLUDED.state,
+                    message    = EXCLUDED.message,
+                    updated_at = EXCLUDED.updated_at
+            """),
+            {"serial": device_serial, "subsystem": subsystem, "state": state, "message": message},
+        )
+        await session.commit()
+
+
+async def delete_alert(device_serial: str, subsystem: str):
+    async with AsyncSessionLocal() as session:
+        await session.execute(
+            text("DELETE FROM device_alerts WHERE device_serial = :serial AND subsystem = :subsystem"),
+            {"serial": device_serial, "subsystem": subsystem},
+        )
+        await session.commit()
+
+
+async def get_alerts(device_serial: str) -> list:
+    async with AsyncSessionLocal() as session:
+        result = await session.execute(
+            text("""
+                SELECT id, device_serial, subsystem, state, message,
+                       updated_at AT TIME ZONE 'UTC' AS updated_at
+                FROM device_alerts
+                WHERE device_serial = :serial
+                ORDER BY updated_at DESC
+            """),
+            {"serial": device_serial},
+        )
+        rows = result.mappings().all()
+
+    return [_row_to_dict(r) for r in rows]
+
+
+# ---------------------------------------------------------------------------
+# Partition management
+# ---------------------------------------------------------------------------
+
+async def ensure_current_partitions():
+    """Create device_logs partitions for the current and next month if missing."""
+    async with AsyncSessionLocal() as session:
+        for month_offset in (0, 1):
+            d = date.today().replace(day=1) + relativedelta(months=month_offset)
+            partition_name = f"device_logs_{d.strftime('%Y_%m')}"
+            start = d.isoformat()
+            end = (d + relativedelta(months=1)).isoformat()
+            await session.execute(text(f"""
+                CREATE TABLE IF NOT EXISTS {partition_name}
+                PARTITION OF device_logs
+                FOR VALUES FROM ('{start}') TO ('{end}')
+            """))
+        await session.commit()
+    logger.info("Partition check complete")
+
+
+async def drop_old_partitions(keep_months: int = 6):
+    """Drop device_logs partitions older than keep_months."""
+    cutoff = date.today().replace(day=1) - relativedelta(months=keep_months)
+    async with AsyncSessionLocal() as session:
+        result = await session.execute(text("""
+            SELECT tablename FROM pg_tables
+            WHERE schemaname = 'public'
+              AND tablename LIKE 'device_logs_%'
+        """))
+        partitions = [r[0] for r in result.fetchall()]
+
+    for name in partitions:
+        # name format: device_logs_YYYY_MM
+        parts = name.split("_")
+        if len(parts) != 4:
+            continue
+        try:
+            partition_date = date(int(parts[2]), int(parts[3]), 1)
+        except ValueError:
+            continue
+        if partition_date < cutoff:
+            async with AsyncSessionLocal() as session:
+                await session.execute(text(f"DROP TABLE IF EXISTS {name}"))
+                await session.commit()
+            logger.info(f"Dropped old partition: {name}")
+
+
+async def partition_manager_loop():
+    """Runs once on startup, then monthly thereafter."""
+    await ensure_current_partitions()
+    while True:
+        # Sleep ~30 days, wake up and ensure next month's partition exists
+        await asyncio.sleep(30 * 24 * 3600)
+        try:
+            await ensure_current_partitions()
+            await drop_old_partitions()
+        except Exception as e:
+            logger.error(f"Partition manager error: {e}")
+
+
+# ---------------------------------------------------------------------------
+# Cleanup (replaces SQLite purge_loop — now a no-op since Postgres uses
+# partition drops instead of row-by-row deletes for device_logs; heartbeats
+# and commands are still purged by row deletion)
+# ---------------------------------------------------------------------------
+
+async def purge_old_data(retention_days: int | None = None):
+    days = retention_days or settings.mqtt_data_retention_days
+    cutoff = datetime.now(timezone.utc) - timedelta(days=days)
+    async with AsyncSessionLocal() as session:
+        await session.execute(
+            text("DELETE FROM heartbeats WHERE received_at < :cutoff"),
+            {"cutoff": cutoff},
+        )
+        await session.execute(
+            text("DELETE FROM commands WHERE sent_at < :cutoff"),
+            {"cutoff": cutoff},
+        )
+        await session.commit()
+    logger.info(f"Purged heartbeats and commands older than {days} days")
+
+
+async def purge_loop():
+    while True:
+        await asyncio.sleep(86400)
+        try:
+            await purge_old_data()
+        except Exception as e:
+            logger.error(f"Purge failed: {e}")
+
+
+# ---------------------------------------------------------------------------
+# Stub — no longer needed but kept so nothing that imports init_db/close_db breaks
+# ---------------------------------------------------------------------------
+
+async def init_db():
+    """No-op: Postgres schema is managed by Alembic, not runtime init."""
+    logger.info("Postgres MQTT backend active — no SQLite init needed")
+
+
+async def close_db():
+    """No-op: SQLAlchemy engine lifecycle is managed by the process."""
+
+
+# ---------------------------------------------------------------------------
+# Helpers
+# ---------------------------------------------------------------------------
+
+def _row_to_dict(row) -> dict:
+    """Convert a SQLAlchemy RowMapping to a plain dict with ISO string timestamps."""
+    d = dict(row)
+    for key, val in d.items():
+        if isinstance(val, datetime):
+            d[key] = val.isoformat()
+    return d
diff --git a/backend/main.py b/backend/main.py
index c55fde0..543762d 100644
--- a/backend/main.py
+++ b/backend/main.py
@@ -108,9 +108,9 @@ async def crm_poll_loop():
 @app.on_event("startup")
 async def startup():
     init_firebase()
-    await db.init_db()
     await melody_service.migrate_from_firestore()
     mqtt_manager.start(asyncio.get_event_loop())
+    asyncio.create_task(db.partition_manager_loop())
     asyncio.create_task(db.purge_loop())
     asyncio.create_task(nextcloud_keepalive_loop())
     asyncio.create_task(crm_poll_loop())
@@ -125,7 +125,6 @@ async def startup():
 @app.on_event("shutdown")
 async def shutdown():
     mqtt_manager.stop()
-    await db.close_db()
     await close_nextcloud_client()
 
 
diff --git a/backend/mqtt/router.py b/backend/mqtt/router.py
index b1b885f..3ddb2d4 100644
--- a/backend/mqtt/router.py
+++ b/backend/mqtt/router.py
@@ -129,27 +129,29 @@ async def mqtt_websocket(websocket: WebSocket):
 
     try:
         from auth.utils import decode_access_token
-        from shared.firebase import get_db
+        from sqlalchemy import select
+        from database.postgres import AsyncSessionLocal
+        from staff.orm import Staff
+
         payload = decode_access_token(token)
         role = payload.get("role", "")
 
         # sysadmin and admin always have MQTT access
         if role not in ("sysadmin", "admin"):
-            # Check MQTT permission for editor/user
             user_sub = payload.get("sub", "")
-            db_inst = get_db()
-            if db_inst:
-                doc = db_inst.collection("admin_users").document(user_sub).get()
-                if doc.exists:
-                    perms = doc.to_dict().get("permissions", {})
-                    if not perms.get("mqtt", False):
-                        await websocket.close(code=4003, reason="MQTT access denied")
-                        return
-                else:
-                    await websocket.close(code=4003, reason="User not found")
-                    return
-            else:
-                await websocket.close(code=4003, reason="Service unavailable")
+            async with AsyncSessionLocal() as session:
+                result = await session.execute(
+                    select(Staff).where(Staff.id == user_sub).limit(1)
+                )
+                staff = result.scalar_one_or_none()
+
+            if staff is None:
+                await websocket.close(code=4003, reason="User not found")
+                return
+
+            perms = staff.permissions or {}
+            if not perms.get("mqtt", {}).get("access", False):
+                await websocket.close(code=4003, reason="MQTT access denied")
                 return
     except Exception:
         await websocket.close(code=4001, reason="Invalid token")
diff --git a/strategies/DATABASE_MIGRATION.md b/strategies/DATABASE_MIGRATION.md
index 23bc638..0f8c4c3 100644
--- a/strategies/DATABASE_MIGRATION.md
+++ b/strategies/DATABASE_MIGRATION.md
@@ -402,12 +402,17 @@ await log_action(db, actor_id, actor_name, "UPDATE", "customer", id, label, chan
 ---
 
 ## Phase 5 — MQTT Live Data Cutover
-**Status: NOT STARTED**
-**Prerequisite:** Phase 1 complete (device_logs in Postgres)
+**Status: COMPLETE** — Postgres live ingestion + partition manager active 2026-04-17
 
-This phase switches the **live MQTT ingestion** from SQLite to Postgres.
+### What changed
+- New `backend/database/pg_mqtt.py` — all MQTT functions rewritten for Postgres (raw SQL, no ORM)
+- `database/__init__.py` — re-exports from `pg_mqtt` instead of `core`
+- `main.py` — removed `db.init_db()` / `db.close_db()`, added `db.partition_manager_loop()`
+- `mqtt/router.py` WebSocket auth — reads from Postgres `staff` table instead of Firestore `admin_users`
+- `device_logs` partitioned writes, `heartbeats`/`commands` as plain tables
+- `purge_loop` still runs for heartbeats/commands; device_logs purged via partition drops
 
-### Steps
+### Steps (original plan, now implemented)
 1. Update `database/core.py` `insert_log`, `insert_heartbeat`, `insert_command` to write to Postgres
 2. Update read functions (`get_logs`, `get_heartbeats`, etc.) similarly
 3. The partition management background job: each month, at startup or via a cron, ensure next month's partition exists:
@@ -470,7 +475,7 @@ backend/
 | 2     | Firestore → Postgres (data migration) | **COMPLETE** — all 5 scripts ran successfully on VPS 2026-04-17 |
 | 3     | Staff auth cutover | **COMPLETE** — Postgres auth live 2026-04-17 |
 | 4     | Audit log system | **COMPLETE** — shared/audit.py live, wired into auth + staff 2026-04-17 |
-| 5     | MQTT live data cutover | NOT STARTED |
+| 5     | MQTT live data cutover | **COMPLETE** — Postgres live ingestion + partition manager 2026-04-17 |
 
 Update this table as each phase completes.