MockDojo

Question bank, System design, Most-asked system design

Design search for a social network

Design full-text search over posts that shows new posts within seconds.

45 minutes, for mid-level, senior engineers

How the interview runs

  1. 1.Requirements. Before we design anything: what are the core functional requirements, and which non-functional ones matter most here?
  2. 2.Estimates. Let's size it. Assume 500M new posts a day and 50K searches per second.
  3. 3.API + data model. What does the API look like, and how would you model and store the data?
  4. 4.High-level design. Walk me through the high-level architecture, request by request.
  5. 5.Deep dive. How do you index fast enough that a post is searchable seconds after it's written?
  6. 6.Trade-offs + failure. What are the main trade-offs you made, and what happens when a component fails?

What you're graded on

  • Clarified requirements15 pts
  • Back-of-envelope estimates10 pts
  • Clear API10 pts
  • Data model + storage choice15 pts
  • Coherent architecture15 pts
  • Real-time inverted index20 pts
  • Trade-offs8 pts
  • Failure handling7 pts

Practice this one for real

Answer it phase by phase, then get the rubric score, what you missed and the model answer outline.

Unlock with Lifetime