How do you reduce allocations in a JSON-heavy API?
PICTURE THIS: DJANGO MVT
Simple meaning
Prefer System.Text.Json source generation, reuse buffers, and avoid ToList on huge graphs.
WHY — Performance instead of guessing?
Why interviewers care about Performance:
question about Performance.
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:
- 1Prefer System.Text.Json source generation,
reuse buffers, and avoid ToList on huge graphs.
- 2Why it exists
Profiling with dotnet-trace beats guessing.
- 3Sometimes pagination is the
real fix.
- 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
Prefer System.Text.Json source generation, reuse buffers, and avoid ToList on huge graphs. Profiling with dotnet-trace beats guessing.