fix(adminmanual): Clarify frequently asked db replica questions

[ChristophWurst]

☑️ Resolves

Clarifies the database replication page (admin_manual/configuration_database/replication.rst) to answer the
questions admins frequently ask about read-only replicas:

• how read vs. write queries are distinguished and routed (reads → replica, writes → primary)
• the read-your-writes consistency guarantee and that it is scoped to a single PHP process (one web request, cron
  run, or occ invocation)
• why the feature needs negligible replication lag, and works best with a synchronous cluster such as Galera
• that Nextcloud only routes to the endpoints you provide — provisioning, syncing and monitoring replication is the
  DBA's job
• that a replica is chosen at random, with no weighting or health checks

🖼️ Screenshots

✅ Checklist

• I have built the documentation locally and reviewed the output
• Screenshots are included for visual changes
• I have not moved or renamed pages (or added a redirect if I did)
• I have run codespell or similar and addressed any spelling issues

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📄 1 changed documentation page

• admin_manual/configuration_database/replication.rst

Last updated: Mon, 24 Aug 2026 11:01:45 GMT