PhonePe system design interview questions

Which levels get a design round

Design questions candidates report

• Product catalog search with sponsored ranking (machine coding)

  Design an online store where millions browse and thousands check out every minute. Requirements and scale, the shopping API and data model, then the hard parts: a read-optimized catalog with search and caching, a cart in a key-value store, inventory reservations that never oversell, a checkout saga with idempotent payments and an outbox, the order state machine, and where you can be eventually consistent.

  Full walkthrough: E-commerce (Amazon)

• Web search engine

  Design a web search engine that answers hundreds of thousands of queries a second over tens of billions of pages. Requirements and scale, the search API and index data model, building a document-partitioned inverted index, a fresh tier for news, scatter-gather query serving with tail-latency tricks, multi-stage ranking with link-based signals, caching, failure handling and the trade-offs.

  Full walkthrough: Google Search

• Real-time cluster monitoring

  How to design a metrics monitoring and alerting system for a hundred thousand machines: collecting samples by pull or push, a buffered write path, a time-series database with compressed chunks and an inverted label index, the cardinality trap, downsampling for long ranges, rule evaluation with pending periods, an alert manager that groups and silences, and how to monitor the monitor.

  Full walkthrough: Monitoring and alerting

Also reported

• Customer issue resolution system (machine coding)
• In-memory to-do list with analytics (machine coding)
• Multi-tenant Q&A platform

How to answer any design question: the LADDER method · How the design round is scored by level · Low-level design and machine coding

Questions people ask