Building a web application that works for 100 users is very different from building one that works for 100,000. Scalability needs to be designed in from the start, not bolted on later.
Foundations of Scalable Architecture
Understanding Scalability
Scalability refers to a system's ability to handle increased load by adding resources. There are two types:
For modern web applications, horizontal scaling is typically the goal, as it offers better fault tolerance and cost efficiency.
Key Principles
1. Stateless Application Design
- Your application servers should not store session data locally. Instead, use:
- Redis or Memcached for session storage
- JWT tokens for authentication
- External storage for user uploads
2. Database Design for Scale
3. Caching Strategy
- Implement caching at multiple levels:
- Browser caching for static assets
- CDN for global content delivery
- Application-level caching
- Database query caching
Modern Architecture Patterns
Microservices
- Breaking your application into smaller, independently deployable services offers:
- Independent scaling
- Technology flexibility
- Fault isolation
- Easier maintenance
Serverless Functions
For certain workloads, serverless can provide automatic scaling with minimal operational overhead.
Event-Driven Architecture
Using message queues and event buses to decouple services allows for better scalability and resilience.
Technology Recommendations
Frontend
Backend
Infrastructure
Monitoring and Observability
- You can't scale what you can't measure. Implement:
- Application performance monitoring
- Infrastructure metrics
- Log aggregation
- Distributed tracing
Conclusion
Building scalable applications requires upfront planning and continuous iteration. Start with good fundamentals, monitor your system, and scale components as needed.
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