The Art of System Design

System design is often taught as a set of blueprints, but in reality, it's the art of managing trade-offs. There is no "perfect" architecture—only the one that best fits your current constraints and future growth.

The Foundation: CAP and PACELC

Most engineers are familiar with the CAP Theorem (Consistency, Availability, Partition Tolerance), but in the real world, PACELC is a more useful mental model. It asks: In the case of a partition (P), how do you trade off availability (A) and consistency (C)? Else (E), when the system is running normally, how do you trade off latency (L) and consistency (C)?

Designing for the "normal" case is just as important as designing for the failure case.

Scalability: Thinking Beyond "Add More Nodes"

While horizontal scaling is the industry standard, it's not always the right first move.

• Vertical Scaling is often simpler and more cost-effective for a long time.
• Database Sharding introduces massive complexity. Before you shard, consider if Read Replicas or Caching (Redis/Memcached) can solve your throughput issues.

State Management: The Root of All Evil

The hardest part of any system is managing state. Stateless services are trivial to scale; databases and distributed caches are not. Always ask: "Does this component really need to be stateful?" If the answer is yes, ensure you have a clear plan for consistency and recovery.

Conclusion

Systems aren't built; they're evolved. Start with the simplest architecture that meets your reliability requirements and add complexity only when the data proves it's necessary.