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System Design Fundamentals

Core system design concepts for technical interviews in 2026: scaling, caching, consistency models, load balancing, database design, rate limiting, back-of-the-envelope estimation, and distributed systems primitives.

System Design Fundamentals

Vertical vs horizontal scaling

Latency vs throughput

Availability vs consistency — CAP theorem

ACID vs BASE

Single point of failure and redundancy

Stateless vs stateful services

Role of message queues in architecture

Consistency models — strong, eventual, read-your-writes, monotonic

Load balancing algorithms

Caching strategies — write-through, write-behind, cache-aside, read-through

Cache invalidation strategies

CDN — push vs pull

Database replication — primary-replica and multi-primary

Database sharding and partitioning

SQL vs NoSQL — selection criteria

Rate limiting algorithms

Back-of-the-envelope estimation

API gateway — full responsibilities and design

Distributed locking

Bloom filters

Idempotency keys — design and implementation

Data storage tiers and hot/warm/cold architecture