diff --git a/backend/app/tasks/backup.py b/backend/app/tasks/backup.py
index 57d8157..77ad1f0 100644
--- a/backend/app/tasks/backup.py
+++ b/backend/app/tasks/backup.py
@@ -41,7 +41,11 @@ def _mark_failed(session, row: BackupRun, exc: BaseException) -> None:
     bind=True,
     autoretry_for=(OperationalError, DBAPIError),
     retry_backoff=10, retry_backoff_max=120, max_retries=2,
-    soft_time_limit=600, time_limit=720,
+    # A pg_dump can't be chunked; the 12-min limit timed out once the DB grew
+    # (operator-flagged 2026-06-07). 30/35 min gives real headroom. (A long
+    # backup still briefly holds the concurrency-1 maintenance lane — the
+    # structural fix is a dedicated lane for the long one-shots.)
+    soft_time_limit=1800, time_limit=2100,
 )
 def backup_db_task(self, *, tag: str | None = None,
                    triggered_by: str = "manual") -> dict:
diff --git a/docker-compose.yml b/docker-compose.yml
index b8da8cd..f292640 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -21,6 +21,11 @@ services:
 
   postgres:
     image: pgvector/pgvector:pg16
+    # Docker's default /dev/shm is 64MB; VACUUM (ANALYZE) and parallel queries
+    # allocate larger shared-memory segments and fail with
+    # "could not resize shared memory segment ... No space left on device"
+    # (operator-flagged 2026-06-07, vacuum_analyze on import_task needed 67MB).
+    shm_size: 512m
     environment:
       POSTGRES_USER: ${DB_USER:-fabledcurator}
       POSTGRES_PASSWORD: ${DB_PASSWORD:-fabledcurator_dev}