Database pool and timeout tuning

The application PostgreSQL engine uses SM_DB_POOL_TIMEOUT=30 seconds to wait for a pooled connection and SM_DB_CONNECT_TIMEOUT=10 seconds to connect. SM_DB_STATEMENT_TIMEOUT_MS=0 and SM_DB_IDLE_IN_TX_TIMEOUT_MS=0 omit their PostgreSQL startup parameters; positive values set limits in milliseconds. All four settings require a process restart. SQLite ignores these settings, including pool timeout. Alembic and the pre-app settings read do not use them.

Set asyncpg timeouts through the host settings, not URL query parameters. Asyncpg receives server settings; psycopg/psycopg2 receive libpq startup options. PgBouncer transaction pooling rejects startup parameters such as these timeout settings. Leave the millisecond settings at zero and configure limits on the server or database role when using that mode.

Background workers inherit the resolved host timeouts. Their sync engine and each outbox thread's async engine have separate pools, defaulting to size 2, overflow 3 and recycling after 1800 seconds. Size the database connection budget for all processes and outbox threads. Override these through SM_BG_TASKS_DB_POOL_SIZE, SM_BG_TASKS_DB_MAX_OVERFLOW and SM_BG_TASKS_DB_RECYCLE. Optional SM_BG_TASKS_DB_STATEMENT_TIMEOUT_MS overrides the host statement limit, including zero to omit it. Restart workers after changing these settings.