chore(docker): default the dev replica apply delay to a realistic 20ms

150ms is useful for deliberately shaking out replica races but is an
order of magnitude above typical streaming-replication lag; 20ms keeps
the local replica honest by default. Override via REPLICA_APPLY_DELAY.

Author: ericallam

docker/docker-compose.yml

@@ -58,7 +58,8 @@ services:
   #   docker exec database bash -c 'grep -q "host replication" "$PGDATA/pg_hba.conf" || echo "host replication all all md5" >> "$PGDATA/pg_hba.conf"'
   #   docker exec database psql -U postgres -c "SELECT pg_reload_conf()"
   # Then point the webapp at it: DATABASE_READ_REPLICA_URL=postgresql://postgres:postgres@localhost:5433/postgres
-  # Tune the lag via REPLICA_APPLY_DELAY (e.g. 150ms, 2s). Wipe database-replica-data to re-init.
+  # Tune the lag via REPLICA_APPLY_DELAY (default 20ms ~ realistic prod lag; crank to 150ms/2s to
+  # shake out replica races). Wipe database-replica-data to re-init.
   database-replica:
     container_name: ${CONTAINER_PREFIX:-}database-replica
     profiles: ["replica"]
@@ -72,7 +73,7 @@ services:
       - ${DB_REPLICA_VOLUME:-database-replica-data}:/var/lib/postgresql/data/
     environment:
       PGPASSWORD: postgres
-      REPLICA_APPLY_DELAY: ${REPLICA_APPLY_DELAY:-150ms}
+      REPLICA_APPLY_DELAY: ${REPLICA_APPLY_DELAY:-20ms}
     networks:
       - app_network
     ports: