System design interviews test your ability to build scalable, fault-tolerant distributed systems under real-world constraints. Candidates often stumble not because of technical ignorance, but due to unstructured thinking.
- Scope & Constraints (5 mins): Clarify functional requirements, DAU, read/write ratios, and latency SLA.
- Capacity Math (5 mins): Calculate QPS, peak throughput, storage per year, and network egress bandwidth.
- High-Level Architecture (15 mins): Draw API gateway, stateless microservices, message queues, and primary databases.
- Deep-Dive & Bottlenecks (20 mins): Address caching strategy, database sharding keys, replication lag, and single points of failure.
1. Never Skip Non-Functional Requirements
Before drawing boxes, ask clarifying questions: Is the system read-heavy (like Twitter/Instagram) or write-heavy (like Uber location telemetry)? Do we prioritize strong consistency (banking ledger) or high availability and eventual consistency (feed generation)?
2. Database Partitioning & Sharding Strategy
When data outgrows a single relational instance, horizontal sharding is essential. Choose your shard key carefully to prevent hotspotting. For example, partitioning solely by user ID balances writes uniformly, but querying across groups requires scatter-gather lookups.
3. Multi-Tier Caching Architecture
Employ Redis or Memcached clusters with read-through or cache-aside semantics. Always define clear TTLs and eviction policies (such as LRU or LFU) to prevent stale cache drift and thundering herd stampedes.
Simulate Live Architecture Rounds with Staff Engineers
Get grilled on real FAANG system design interview problems with immediate, detailed grading on scalability, trade-off explanations, and edge-case handling.
