Opening Scenario
Your product is growing. The database server is handling 90% reads — product listings, search results, user profile pages — and 10% writes — orders, profile updates, stock adjustments. CPU on the database is consistently above 80%. Reads and writes are competing for the same hardware.
Your first instinct is to upgrade the instance. But your infrastructure lead says "add a read replica instead." You've heard the term but never set one up. You're not sure what it actually does, what it doesn't do, and whether your application needs to change.
Question Progression
Q1: What problem does a read replica solve — and what problem does it not solve?
Question: Your CPU is 80% utilized, mostly from SELECT queries. If you add a second database server and route reads to it, where does the data come from, and what's the catch?
Reasoning: The second server needs data that's current enough to be…
In the full tutorial
- Closing: When to Reach for This