We can’t survive Backend if you don’t know these concepts

Here’s a clean short description cheat sheet for all 5 backend concepts

#1 Authentication & Authorization

• Authentication – Verifies who the user is (login).
• Authorization – Decides what the user can access.
• Real-world example – Login (auth) + access control (authorization).
• Login methods – JWT (token), Session (server-based), OAuth (third-party login).
• Roles & Permissions – Define user access levels (admin, user, etc.).
• Middleware protection – Secures routes before request reaches logic.

#2 Caching Strategies

• Cache Aside – App checks cache first, then DB if needed.
• Write Through – Data written to cache and DB together.
• Write Back – Cache updated first, DB updated later.
• Read Through – Cache handles fetching data automatically.

#3 API Design & Rate Limiting

• REST vs GraphQL – REST = multiple endpoints, GraphQL = flexible queries.
• Designing APIs – Structure endpoints clearly and consistently.
• HTTP Methods & Status Codes – GET, POST, PUT, DELETE + 200, 404, etc.
• Rate Limiting – Restricts number of requests per user.
• Implementing Limits – Use tools/middleware to control traffic.
• Common Solutions – Token bucket, fixed window, sliding window.

#4 Load Balancing & Scaling

• Load Balancing – Distributes traffic across servers.
• Horizontal vs Vertical Scaling – More machines vs stronger machine.
• Algorithms – Round Robin, Least Connections, IP Hash.
• DNS-based Balancing – Uses DNS to distribute traffic globally.
• Health Checks – Detects and removes unhealthy servers.
• Balancer Config – Setup rules for traffic routing.

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#5 Environment & Secret Management

• .env files – Store sensitive configs separately.
• Environment Variables – Runtime config values for apps.
• Secret Management Tools – Secure storage for secrets (Vault, AWS).
• Using .env in Code – Load env variables via libraries.
• Local vs Production Secrets – Different configs for different environments.
• Best Practices – Don’t expose secrets, use encryption & access control.