System design interviews for senior and lead software engineering roles evaluate how you balance latency, consistency, availability, and cost under scale. This primer arms you with the core building blocks to design services capable of handling millions of requests per second.
Horizontal Sharding & Consistent Hashing
When single database instances exceed storage or IOPS limits, horizontal sharding distributes data across discrete database shards. Learn how consistent hashing with virtual nodes minimizes data migration during cluster scale-out operations.
Distributed Rate Limiting with Redis & Token Buckets
Protect critical upstream microservices from cascading failures and abusive traffic. We break down token bucket and sliding window counter algorithms executed via atomic Redis Lua scripts to maintain microsecond validation latency.
CQRS and Read Replicas
Separating read queries from write commands through Command Query Responsibility Segregation (CQRS) allows read-heavy applications to scale independently with asynchronous replication pipelines.