Most systems don’t start distributed. They start simple and evolve with scale.
Here’s the typical flow.
1. Single Server
Everything runs on one machine:
- application
- database Easy to build, easy to break.
2. Split Application and Database
Move database to a separate server.
Benefits:
- better performance
- independent scaling
3. Horizontal Scaling
Add multiple application servers.
Now the system can handle more traffic.
Problem:
How do users reach the right server?
4. Load Balancer
Distributes incoming requests across servers.
Benefits:
- avoids overload
- improves availability
5. Database Replication
Primary database handles writes
Replicas handle reads
Benefits:
- reduces load on primary
- improves read performance
6. Caching
Use Redis or in-memory cache.
Store:
- frequently accessed data
- session data Benefits:
- faster responses
- fewer database queries
7. CDN
Serve static files closer to users.
Benefits:
- lower latency
- reduced backend load
8. Message Queue
Use queues for async work:
- emails
- notifications
- background jobs Benefits:
- decouples system
- improves reliability
9. Database Sharding
Split data across multiple databases.
Benefits:
- handles large scale Tradeoff:
- added complexity
10. Monitoring
Track:
- latency
- errors
- traffic Without this, you are blind.
Key Idea
Systems are not designed for scale from day one. They evolve as bottlenecks appear.
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