It's 90% about understanding the problem at hand.

Here's how to scale smart:

If you know you have a high read ratio vs. a low write ratio.

• Separate those services so they can scale differently.

For instance, in an e-commerce application, you might have a service for handling search queries (reads) and a separate service for updating product details (writes).

• Improve performance at the storage level.

You can set up 1 write DB, and 3 read replicas in a master-slave replication setup.

The master handles all write operations, and the replicas handle read operations.

• Add a cache layer.

You can cache product details or repeated queries.

This will reduce the load on the database by serving frequently accessed data from memory.

Getting better business knowledge is the only way to have the right design.