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Understanding HTTP Status Codes: A Complete Guide

A comprehensive introduction to HTTP status codes — what they are, how they're organized into classes (1xx-5xx), and why they matter.

HTTP Redirects: 301 vs 302 vs 307 vs 308

When to use each redirect status code and how they affect SEO, caching, and HTTP method preservation.

HTTP Caching: Cache-Control, ETags, and 304 Responses

How HTTP caching works end-to-end — from Cache-Control directives to conditional requests and 304 Not Modified responses.

Complete Guide to HTTP Methods: GET, POST, PUT, PATCH, DELETE

An in-depth look at HTTP request methods — their semantics, safety, idempotency, and when to use each one in web applications and APIs.

Essential HTTP Headers Every Developer Should Know

A practical reference to the most important HTTP headers — request headers, response headers, caching headers, and security headers.

HTTP/2 vs HTTP/3: What Changed and Why

A comparison of HTTP/1.1, HTTP/2, and HTTP/3 — multiplexing, header compression, QUIC transport, and real-world performance differences.

Choosing the Right HTTP Status Codes for REST APIs

Practical guide to selecting appropriate status codes for API responses — from CRUD operations to error handling.

gRPC Status Codes: A Practical Guide

How gRPC status codes map to HTTP codes, when to use each one, and how to handle errors in gRPC services.

How to Implement and Handle Rate Limiting (429)

Everything about rate limiting — server-side implementation strategies, client-side handling, and the 429 Too Many Requests response.

API Versioning Strategies: URL, Header, and Query Param

How to version your API without breaking existing clients — comparing URL path, custom header, and query parameter approaches.

Designing Consistent API Error Responses

How to build a consistent error response format for your API — status codes, error objects, validation errors, and RFC 7807 Problem Details.

Debugging 502 Bad Gateway Errors

Step-by-step troubleshooting guide for 502 Bad Gateway errors — from reverse proxy misconfiguration to upstream server crashes.

Debugging CORS Errors: A Developer's Guide

Why CORS errors happen and how to fix them — from missing headers to preflight request failures.

Debugging Timeout Errors: 408 and 504

Understanding and fixing HTTP 408 Request Timeout and 504 Gateway Timeout errors in production systems.

Debugging 503 Service Unavailable Errors in Production

A systematic approach to diagnosing 503 errors — server overload, deployment issues, health check failures, and auto-scaling gaps.

TLS/SSL Certificate Troubleshooting Guide

How to diagnose and fix SSL/TLS certificate errors — expired certificates, chain issues, mixed content, and cipher mismatches.

Step-by-Step DNS Troubleshooting with dig and nslookup

A systematic approach to debugging DNS problems — resolution failures, propagation delays, NXDOMAIN errors, and DNSSEC issues.

401 Unauthorized vs 403 Forbidden: When to Use Each

The definitive guide to the most commonly confused HTTP status codes — authentication vs authorization errors.

Essential HTTP Security Headers

A guide to the most important security headers every web application should implement — HSTS, CSP, and more.

OAuth 2.0 Flows Explained: Authorization Code, Client Credentials, PKCE

A practical guide to OAuth 2.0 — when to use each grant type, how the flows work, and security considerations for web apps, SPAs, and machine-to-machine auth.

JSON Web Tokens: Structure, Signing, and Common Pitfalls

Everything developers need to know about JWTs — the three-part structure, signing algorithms, token validation, and security pitfalls to avoid.

API Keys vs OAuth vs JWT: Choosing the Right Auth Method

A comparison of authentication methods for APIs — when to use API keys, OAuth 2.0, or JWTs, with security trade-offs for each approach.

SMTP Reply Codes: What Your Email Server Is Telling You

Understanding SMTP reply codes — from successful delivery (250) to bounce messages (550) and temporary failures (421).

Improving Email Deliverability: SPF, DKIM, and DMARC Setup

A step-by-step guide to setting up email authentication — SPF records, DKIM signing, and DMARC policies to avoid the spam folder.

Diagnosing Email Bounces: Soft (4xx) vs Hard (5xx)

How to read SMTP bounce codes and take the right action — temporary vs permanent failures, common bounce reasons, and list hygiene.

DNS Response Codes (RCODEs) Explained

Understanding DNS RCODEs — from NOERROR and NXDOMAIN to SERVFAIL and REFUSED, with dig command examples.

FTP Reply Codes: Understanding File Transfer Responses

A practical guide to FTP reply codes — from successful transfers (226) to login failures (530) and permission denied (550).

DNS TTL: How to Set TTL Values and Avoid Propagation Delays

Everything about DNS Time-To-Live — how TTL affects caching, what values to use for different record types, and how to plan migrations.

WebSocket Close Codes: Why Your Connection Dropped

Understanding WebSocket close status codes — from normal closure (1000) to protocol errors (1002) and abnormal disconnects (1006).

SIP Response Codes: Understanding VoIP Call Flow

How SIP response codes drive VoIP call setup, ringing, busy signals, and call failures.