How do you design EF Core migrations for zero-downtime deploys?
PICTURE THIS: HOW TO EXPLAIN IT
Simple meaning
Expand then contract: add nullable columns, dual-write, backfill, switch reads, drop later.
WHY — EF Core instead of guessing?
Why interviewers care about EF Core:
question about EF Core.
trade-offs, and what you would actually do on a .NET 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:
- 1Expand then contract: add
nullable columns, dual-write, backfill, switch reads, drop later.
- 2Breaking renames in one
deploy take the site down.
- 3I keep migrations backward
compatible with the previous app version.
- 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
Expand then contract: add nullable columns, dual-write, backfill, switch reads, drop later. Breaking renames in one deploy take the site down.