API Design · Senior · Question 65 of 75

How can you replace a legacy API with a new implementation without a big-bang switch?

1Ask all clients to migrate before writing the new API
✓Correct answer: Strangler fig: put a routing layer in front, move endpoints to the new service one by one, compare responses, and retire the old ones gradually
3Turn off the old API and launch the new one the same day

Explanation

Shadowing traffic to the new implementation and diffing responses builds confidence before switching each route.

Further reading

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