Postgres error

Updated 11 October 2026

Short answer

PostgreSQL errors say plainly what went wrong, so read the message. "Connection refused": Postgres isn't running or isn't listening at that address. Authentication failures, including ones that mention pg_hba.conf: the login or the access rules are wrong. Too many connections (error code 53300): you've used every connection. Statement timeout: a query ran longer than statement_timeout allows. A missing relation (table): usually a migration that didn't run.

What's the problem

Your app fails with a Postgres error in the logs or on screen, often starting with FATAL: or ERROR:.

Why it happens

  • Connection refused: the server is stopped, listening on a different address or port, or blocked by a firewall.
  • Authentication failed: wrong password, or the server's access rules (pg_hba.conf, or a cloud provider's settings) don't allow your app's address or require SSL.
  • Too many clients: connections are leaking or there's no pooling.
  • Statement timeout: a slow query or a lock.
  • Relation does not exist: migrations didn't run on this database, or the app is pointed at the wrong one.
  • Disk full or out of memory on the database server.

How to fix it

  1. Copy the exact error message from your app's logs.
  2. For "connection refused", check the database is running and the host and port in your app's settings are right.
  3. For authentication errors, check the password and the access rules in pg_hba.conf (or your cloud provider's settings); many cloud databases require SSL connections.
  4. For too many connections, see too many connections.
  5. For timeouts, see database timeout.
  6. For missing relations, run your migrations against the live database and check the connection string points to the right one.

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Sources

  1. PostgreSQL: Connections and Authenticationofficial docsWhenever the number of active concurrent connections is at least max_connections minus superuser_reserved_connections , new connections will be accepted only for superusers.
  2. PostgreSQL: Client Connection Defaultsofficial docsAbort any statement that takes more than the specified amount of time.
  3. PostgreSQL: The pg_hba.conf Fileofficial docsClient authentication is controlled by a configuration file, which traditionally is named pg_hba.conf and is stored in the database cluster's data directory.
  4. PostgreSQL: PostgreSQL Error Codesofficial docs53300 too_many_connections

Related

Database connection error Your app can't reach its database: the database is stopped, the address or password is wrong, or a firewall is blocking it. Check them in that order. "Too many connections" database error Every database connection is in use. Usually your app opens connections and doesn't close them, or traffic outgrew the limit. Fix leaks first. Database timeout A query or connection took longer than allowed: usually a slow query on a big table, a missing index, locked rows, or an overloaded database. MySQL error Read the error number: 1045 is access denied, 2002 means the server isn't reachable, 1040 is too many connections. The MySQL error log says the rest.
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