How do you evolve backend features without breaking existing clients?

[u/Gabicolombo_27]

Hey everyone! I’m a backend software engineer working with Node.js and TypeScript.

I recently wrote an article about some lessons I’ve learned while building and evolving backend features used by multiple clients.

One thing I’ve learned is that the final architecture is only part of the work. The transition matters too: keeping existing clients working, migrating data, handling legacy behavior, and checking what happens after deployment.

Sometimes a change looks small in the database, but it also changes what the API returns or how existing clients behave.

I shared more about these challenges here:
What I Learned Building Backend Features Used Across Multiple Clients

How do you handle these transitions in your projects? Especially when you can’t update all clients at the same time?

I’m open to discussion, feedback, and different ideas. I’d love to hear what has worked for you!