Design status update search with AND/OR
PremiumBackend systemMedium
- Inverted index
- Boolean query
- Posting lists
Quick answer
This backend system interview question asks you to design status update search with AND/OR. Aim for a design that meets its requirements at the stated scale, then explain its main components, data flow and trade-offs. Interviewers want to see how you scope the problem, size it and defend each choice.
The problem
Design a status update search service for a social network where users search short, text-only public status posts with AND, OR and parentheses, such as (pizza OR burger) AND delhi. There is no relevance ranking: matches come back newest first. The hard parts are building the inverted index on the write path fast enough and choosing how to shard it.
What must the system do?
- Boolean search: Accept queries with up to 10 terms joined by AND, OR and parentheses, with AND binding tighter than OR.
- Newest first: Return 20 matching posts per page, newest first, with a cursor for the next page.
How well must it do it?
- Correct matches: Every result satisfies the query, and no match newer than the last returned result is skipped.
- Latency: Search p99 under 300 ms for the first page.
What scale should you design for?
Use these numbers in your estimates.
The scale numbers unlock with this questionUnlock
Key concepts
- Inverted index
- Boolean query
- Posting lists
- Document sharding
- Term sharding
- Write path indexing
How you’ll practise
- Requirements
- Estimate
- API and data
- High-level design
- Deep dives
- Wrap-up
Lala, personalized to you, gives a hint when you ask and reviews your design when you are ready.
What do interviewers look for?
In any backend system design round.
- Clarifies the requirements before drawing anything
- Uses a few numbers that actually change the design
- Draws a clear path from the client to storage
- Picks storage and caching with reasons, not by habit
- Explains what breaks first under load and how to fix it
- States trade-offs openly instead of claiming a perfect design
Questions people ask about this interview question
- Which design type is this question?
- It is a backend system question. You design status update search with AND/OR and explain your choices the way you would in an interview.
- Is this question asked at entry level?
- It is marked Medium. Entry-level engineers can practise it, but it expects you to reason about requirements and trade-offs, not only list components.
- What should I cover first?
- Start with the requirements: what the system must do, how well it must do it and which numbers change the design. Agree on scope with the interviewer before you design anything.
- Can I practise it for free?
- It is a premium question. Sign up and unlock it once for 10 credits; it then stays unlocked. When you finish, Lala, your personalized AI mentor, can review your design for 30 credits.
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Updated · Written by the SevyDevy team