What is a read replica and how does it help with scaling?

Short answer: A read replica is a copy of a database that is used to offload read-only queries from the primary database (master).

Explain a bit more

It is particularly useful for handling high read traffic and improving database scalability. How it helps with scaling: By distributing read requests across multiple replicas, the primary database can focus on write operations, reducing the load on the master. It improves performance by providing additional resources dedicated to read operations. Example: In a web application with high traffic, multiple read replicas can serve read-heavy queries, while writes are only made to the master database. Note: Read replicas are usually asynchronous, meaning there can be a slight delay in replication. For critical real-time reads, this might not be suitable.

Real-world example (ShopNest)

ShopNest’s SQL Server database stores customers, products, and orders. Good indexes and clear foreign keys keep checkout queries fast and safe.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.