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.
A poison customer kills its 2 of 8 workers. Who else goes down?
Build-up · 5 steps
Follow one request through a thin router
One tenant’s request, from key to cell, and then two bad days. The control plane goes down, and a cell fails.
Step 1 of 5
Cells, full copies, nothing shared
Each cell runs the app, workers, caches and its own databases, built from one template and capped at a tested size. Cells share no state and never call each other.
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
“You’re splitting a team-chat product into cells. Which partition key decides who shares a cell?”
Your move. Pick an approach:
Deep dive 2 of 4
Interviewer
“Your SaaS peaks at 90,000 req/s; one cell breaks at 15,000; the largest tenant does 3,000. Where do you cap cells?”
Your move. Pick an approach:
Deep dive 3 of 4
Interviewer
“Inside one cell, eight stateless workers serve every customer. One customer’s requests crash any worker they reach. How do you assign workers?”
Your move. Pick an approach:
Deep dive 4 of 4
Interviewer
“Admins want one search box across every tenant, in every cell. How do you build it?”
Your move. Pick an approach: