How do you design an API for backwards compatibility?
PICTURE THIS: HOW TO EXPLAIN IT
Simple meaning
Additive fields, explicit versioning, and deprecation windows.
WHY — Design instead of guessing?
Why interviewers care about Design:
question about Design.
trade-offs, and what you would actually do on a Backend project - not buzzwords.
Name the idea, why it exists, then one short example.
End with when you use it and one common pitfall.
STEPS — What happens step by step?
Before you speak the answer, walk the interviewer through these steps:
- 1Additive fields, explicit versioning,
and deprecation windows.
- 2Breaking changes need a
new version.
- 3Clients should keep working
during migration.
- 4Give an example
One tiny concrete case you can say aloud.
- 5Common mistake
What juniors usually get wrong.
- 6Close
When you pick this over the alternative.
EXAMPLE — See it in action
Here's a short line you can speak, broken into clear beats:
Note: Adapt this scaffold to your own project — keep it under 60–90 seconds.
Key takeaway
Additive fields, explicit versioning, and deprecation windows. Breaking changes need a new version.