Horizontal vs Vertical Scaling: A Developer's Guide to Choosing the Right Path

A developer recounts scaling a SaaS app from 20 to 2,000 requests per second, comparing vertical scaling (upgrading a single server) and horizontal scaling (adding more servers). The article advises scaling out for stateless, request-driven workloads and scaling up for monolithic or state-bound components. Code examples in Node.js illustrate the transition from a single-instance monolith to a horizontally scalable architecture.