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Scalability is a system's ability to handle growth — more users, more data, more traffic. It's like a restaurant: a small café works for 20 customers, but you need a bigger kitchen and more staff for 200 customers.
Types of Scaling:
- Vertical scaling (scale up): Make one server bigger (more CPU, RAM)
- Horizontal scaling (scale out): Add more servers
Scalability Dimensions:
- Load: Handle more requests per second
- Data: Store and process more data
- Geographic: Serve users in different regions
- Feature: Add new features without breaking existing ones
Why Scalability Matters:
- Growth: Your app might get popular
- Performance: Keep response times fast as you grow
- Cost: Scale efficiently to control costs
- Reliability: Distribute load prevents single points of failure
Scalability Strategies:
- Caching: Reduce database load
- Load balancing: Distribute traffic
- Database sharding: Split data across databases
- CDN: Serve static content globally
- Microservices: Scale services independently
FAQ
When should I think about scalability?
Start simple, but design with scalability in mind. Don't over-engineer, but avoid choices that make scaling impossible later.
Is horizontal scaling always better?
Usually yes for large scale, but vertical scaling is simpler and might be enough. Many systems use both.