Comment by quantumf

I think you're understating how tough it can be.

There are applications that

  * are mature and complex

  * with 100s of tables

  * serving millions of users

  * have to be broken into multiple micro-services

  * have developer resource constraints

So you're easily looking at a 1-2 year project, not 1-8 weeks.

You've also ignored some of the complexities, such as resharding (moving data between shards), which may significantly add to the cost of the project.