Plan

1. Users

• Visitor Users (readers) → access the site to view content (GET).
• Logged-In Users (editors) → access the panel/app to create or modify content (POST, PUT, DELETE).

2. Servers

• WEB Server (read)
  • Serves visitors.
  • Runs Nginx/PHP.
  • When data is needed, performs read-only (SELECT) queries against the Replica Database.
• APP Server (write)
  • Serves logged-in users.
  • Runs Nginx/PHP.
  • Performs write operations (INSERT/UPDATE/DELETE) on the Primary Database.

3. Database

• Primary MySQL (WRITE)
  • Holds N databases, one per domain (db_site1, db_site2, …).
  • All writes go here.
  • Streams changes in real time to the replica.
• Replica MySQL (READ)
  • Exact copy of the primary.
  • Also has N databases (db_site1, db_site2, …).
  • Continuously updated via replication.
  • Responds to visitor read queries.

4. Full Flow

• Visitor → WEB → Replica (SELECT).
• Logged-in User → APP → Primary (INSERT/UPDATE/DELETE).
• Primary → Replica: changes copied immediately (milliseconds/seconds).

👉 Result: