n8n self-host: SQLite or Postgres for a five-person team, and when does queue mode become necessary?Solved

Postgres from day one, even for five people. Not because SQLite breaks at your volume (it would not) but because of three smaller things: execution data grows fast and SQLite gets slow to vacuum; backups of a running SQLite file are fiddly, while pg_dump is boring; and every n8n upgrade note assumes Postgres. The switch later is a documented export/import, but you will do it on a day you did not plan to. DB_TYPE=postgresdb plus the DB_POSTGRESDB_* variables is all it takes.

Queue mode is for when executions wait on each other. The signal is simple: workflows that used to finish in seconds start to finish in minutes while CPU on the box is not the problem. That is the single process serialising. Five people with a few hundred executions a day will not see it. When you do, EXECUTIONS_MODE=queue, a Redis, and one or more n8n worker processes, and the main process stops executing and only schedules.

Day-one variables people regret: EXECUTIONS_DATA_PRUNE=true with EXECUTIONS_DATA_MAX_AGE so the executions table does not grow forever; N8N_ENCRYPTION_KEY set explicitly and backed up, because credentials are encrypted with it and losing it means re-entering every credential; and WEBHOOK_URL set to the public address if you sit behind a proxy, or webhook nodes will show the wrong URL.