title: High-level design (HLD) description: System design for SDE2 interviews: the fundamentals behind every architecture and the case studies interviewers ask for.
High-level design (HLD)¶
System design rounds test whether you can turn a vague product prompt into a justified architecture in 45 minutes. This section has two parts: the fundamentals explain the building blocks and the trade-offs behind them; the case studies apply them to the systems interviewers actually ask for. Work through the P0 fundamentals, then the P0 case studies, then use the mock interviews to rehearse against the clock.
Sections¶
- Fundamentals - 27 pages: the concepts and trade-offs every case study builds on
- Case studies - 31 pages: the systems interviewers ask for, solved end to end
Start here (P0)¶
Fundamentals¶
- The 45-minute HLD framework
- Back-of-envelope estimation
- From one server to millions of users
- Networking for system design
- API design for HLD rounds
- Load balancing, reverse proxies and API gateways
- Caching and CDNs
- Choosing a database
- Replication
- Partitioning, sharding and consistent hashing
- Transactions, 2PC, sagas and idempotency
- CAP, PACELC and consistency models
- Messaging, queues and Kafka internals
- Rate limiting
- Resilience patterns