Layer 3 · Go deeper · 7 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.
How many shard copies does the dinner peak need?
An IPL final’s innings break triples traffic. How many copies, and when?
Build-up · 6 steps
Feed the index, read the truth
Follow one menu change into the dish index, then one “biryani” search back out. Nothing writes to Elasticsearch except the indexer.
Step 1 of 6
Write to the database only
The menu service writes Postgres, the source of truth, and never calls Elasticsearch. Dual writes can crash between the two stores, and two concurrent updates can reach the index in the wrong order.
3 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 3
Interviewer
“A food app searches dishes near the user. Restaurants have about 60 dishes each. How do you model them?”
Your move. Pick an approach:
Deep dive 2 of 3
Interviewer
“As users type, the app shows dishes from open restaurants nearby. Someone types “tikka pa”. Which typeahead do you build?”
Your move. Pick an approach:
Deep dive 3 of 3
Interviewer
“Your B2B SaaS has 50,000 tenants, and each searches only its own documents. How do you lay out the indices?”
Your move. Pick an approach: