Scalability in enterprise software: when to plan for it and when it's just premature optimisation

Premature scalability is the second biggest waste in software development (after software nobody uses). But lack of scalability at the right time can sink a business. The key is knowing when to plan — and when it's too early.

• •Signals you need to plan scalability now: application response time exceeds 3 seconds under normal load, infrastructure costs are spiking without correlation to revenue growth, or you have predictable load spikes that saturate the system.
• •Horizontal vs. vertical scalability: scaling vertically (more CPU/RAM to the server) is simpler but has limits. Scaling horizontally (more instances of the same service) is more complex but theoretically unlimited. Most mid-sized enterprise applications only need vertical scaling.
• •Caching as the first step: 80% of scalability problems are solved with a good caching system (Redis for frequent data, CDN for static assets). Add cache before redesigning the architecture — it's 10x cheaper.

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