System Design Interview Template

REQUIREMENTS [5 min]

1. Functional and non-functional requirements

2. Use cases and scenarios that will not be covered

3. Who are the users

4. What is the expected load

5. Usage patterns

ESTIMATIONS [5 min]

1. Traffic estimates - throughout (QPS), latency

2. Read/Write ratio

3. Storage estimates

4. Memory estimates

DESIGN GOALS [5 min]

1. CP vs AP - weak/eventual/strong consistency

HIGH LEVEL DESIGN [5-10min]

1. Basic system components

2. Database schema

3. API design

4. Use cases flows

DEEP DIVE [15-20min]

1. Scalability and Performance Optimisations

   1. Caching - CDN, cache invalidation, cache eviction policies, expiration policies

   2. API Gateway

   3. Proxies

   4. Databases - SQL vs NoSQL, sharding

   5. Async Processing - message queues, event driven architecture, FSMs, transactional outbox, change data capture, cqrs, saga, 2 phase commit

2. Fault Tolerance and Redundancy

   1. Leader and follower - quorum/consensus

   2. Liveness - heartbeat, gossip protocol, phi accrual failure detection

   3. Resyncing nodes - hinted handoff, merkle trees, read repair

   4. Nodes coming back up - split brain with fencing, split brain with generation clock

   5. WAL

3. Logging, Monitoring, Observability

   1. Metrics to track

   2. Alerts to set up

4. Deployment Strategies

   1. Rolling, blue/green, canary, A/B testing, shadow release

5. Examples of cloud technologies that might be used for the system