Layer 3 · Go deeper · 6 min
Go deeper
Size it, build it, then make the calls an interviewer will push you on.
Back of the envelope
Size it up
Tap through each step of the arithmetic.
At what steady load do two containers beat Lambda?
Build-up · 6 steps
Watch results day hit Lambda
An exam-results portal on Lambda, 100 ms a request, in the first minute after results go live at 10:00.
Step 1 of 6
A normal day: 30 environments
Functions scale in concurrency, requests a second × average duration. A normal peak of 300 requests a second at 100 ms keeps just 30 environments busy.
4 interview moments
You’re the candidate
The interviewer pushes on the hard parts. Pick an approach and see how it holds up.
Deep dive 1 of 4
Interviewer
“Your functions read and write PostgreSQL, and at peak 1,000 run at once. How do they connect?”
Your move. Pick an approach:
Deep dive 2 of 4
Interviewer
“A UPI-style gateway sends payment-success webhooks to your function and resends if you don’t answer quickly. How do you update the order?”
Your move. Pick an approach:
Deep dive 3 of 4
Interviewer
“Your API on Lambda now averages 500 requests a second, steady all day. Do you keep it there?”
Each request runs 100 ms in a 512 MB function.
Your move. Pick an approach:
Deep dive 4 of 4
Interviewer
“A big export takes 2 hours, and your stack is serverless. How do you run it?”
Your move. Pick an approach: