Request flow
01
Users
Clients send requests
→
02
Entry Point
Load balancer / API gateway
→
03
App Services
Stateless business logic
→
04
Data & State
SQL / NoSQL DB
05
Cache / Queue
Speed + async
→
06
Storage
Object / file — durable data
← Select a layer to explore it
Cross-cutting concerns — built into every layer
Security
Auth, encryption
Monitoring & Logging
Observe everything
Scalability
Handle growth
Reliability
Uptime, failover
Maintainability
Modular design
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Core principles
Understand requirements
Know what & why
Break it down
Smaller, manageable parts
Make trade-offs
Balance costs
Design for change
Expect evolution
Iterate & improve
Learn, measure
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