Redis: per-app DB index (0-5) with shared auth DB 15 for SSO keys;
flushdb replaces flushall so deploys don't wipe cross-app auth state.
Postgres: drop 13 cross-domain FK constraints (migration v2t0p8q9r0),
remove dead ORM relationships, add explicit joins for 4 live ones.
Multi-engine sessions (account + federation) ready for per-domain DBs
via DATABASE_URL_ACCOUNT / DATABASE_URL_FEDERATION env vars.
All URLs initially point to the same appdb — zero behaviour change
until split-databases.sh is run to migrate data to per-domain DBs.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
