Nextcloud 35's Database checks flag three Performance issues out of the
box: buffer cache hit ratio ~96% (wants 99%+), 100k+ dead tuples, and
million-plus sequential scans on oc_mail_tags / oc_guests_users.
Root causes in Sovran: stock 128MB shared_buffers, stock 60s autovacuum
naptime, APCu file locking, and db:add-missing-indices running exactly
once at install time (never on upgrades or app installs).
Size Postgres for the README's Server + Desktop recommendation (32 GB
RAM, NVMe): 2GB shared_buffers, 12GB effective_cache_size, 512MB
maintenance_work_mem, 32MB work_mem, 4GB max_wal_size, 30s autovacuum
naptime with 4 workers. shared_buffers stays below the 25% rule because
Postgres shares the box with bitcoind, Electrs, LND, MariaDB and PHP-FPM.
Scope the aggressive autovacuum to nextclouddb via ALTER DATABASE so the
shared matrix-synapse DB keeps the milder cluster defaults.
Add a local Redis (127.0.0.1:6379, Nextcloud only) and move
memcache.distributed/locking to Redis; migrate existing installs with a
one-shot since nextcloud-init never re-runs.
Add a weekly nextcloud-db-maintenance timer (VACUUM ANALYZE +
db:add-missing-*) so upgrades and later app installs can't regress the
checks again.
Note: shared_buffers needs one 'systemctl restart postgresql', which
briefly takes down both Nextcloud and Matrix. Everything else is
reload-only or scoped to nextclouddb.
