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beginnerFree

RESTful API Mastery: The Greybox Approach

Master the language of the web. You don't need to build the backend to understand it. This course transforms beginners into intermediate problem-solvers who can communicate, debug, and exploit APIs using industry-standard tools and a deep understanding of HTTP mechanics. You will learn through a greybox approach: - Understanding REST anatomy (Headers, Params, Body, Cookies, Cache) - Handling security and authorization (API Keys, JWT, Auth flows) - Debugging APIs through input/output analysis without backend access - Mastering tools across GUI (Postman, Insomnia) and CLI (cURL, HTTPie) Two learning paths are available: - Visual Explorer (GUI-driven tools) - Terminal Hacker (CLI & code-driven approach) By the end of this course, you will not just "use APIs" — you will understand how they behave, how they fail, and how to control them.

32 lessons 6h 28m Skill-Wanderer
apirestbackendqadebuggingautomationpostmancurl

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Rei Reltroner — Course Author

About the Author

Rei Reltroner · Full-Cycle Solutions Associate · Software Engineer · API & Security Specialist

A system-focused Software Engineer specializing in modular architecture, secure authentication, and deterministic system design. Experienced in building ERP-scale systems with Laravel, implementing OIDC/SSO (Keycloak), and designing audit-grade financial infrastructures with immutable data models. Contributed to full-cycle product delivery across distributed teams, improving system reliability, scalability, and security posture. Known for bridging backend systems with real-world problem solving through REST APIs, debugging strategies, and production-ready engineering practices. Experienced in building multi-service systems with SSO, CI/CD pipelines, and audit-safe financial reporting.

Published: April 8, 2026 Last updated: April 13, 2026

Course Content

Module 1: REST Anatomy

7 lessons · 1h 20m
01

Introduction to REST API

Lesson 10 min
02

What is REST & Greybox Thinking

Locked
Lesson 10 min
03

HTTP Methods (GET, POST, PUT, DELETE)

Planned
Lesson 12 min
04

Status Codes (200, 201, 400, 401, 404, 500)

Planned
Lesson 10 min
05

Headers Basics

Planned
Lesson 8 min
06

Assignment: Analyze Public API

Planned
Assignment 20 min
07

Quiz: REST Fundamentals

Planned
Lesson 10 min

Module 2: Payload & Meta Locked

5 lessons · 1h 2m
08

JSON Structure Deep Dive

Planned
Lesson 10 min
09

Request Body vs Query Params

Planned
Lesson 10 min
10

Response Structure & Pagination

Planned
Lesson 12 min
11

Assignment: Build Structured Request

Planned
Assignment 20 min
12

Quiz: Payload Understanding

Planned
Lesson 10 min

Module 3: Security Locked

5 lessons · 1h 2m
13

Authentication vs Authorization

Planned
Lesson 10 min
14

Bearer Token & API Key

Planned
Lesson 10 min
15

Common Security Pitfalls

Planned
Lesson 12 min
16

Assignment: Secure API Call

Planned
Assignment 20 min
17

Quiz: API Security

Planned
Lesson 10 min

Module 4: CRUD & Debug Locked

5 lessons · 1h 2m
18

CRUD Operations in Practice

Planned
Lesson 10 min
19

Error Handling Strategy

Planned
Lesson 10 min
20

Debugging API Failures

Planned
Lesson 12 min
21

Assignment: Debug Broken API

Planned
Assignment 20 min
22

Quiz: Debugging

Planned
Lesson 10 min

Module 5: Automation Locked

5 lessons · 1h 4m
23

Intro to API Automation

Planned
Lesson 10 min
24

Using Postman for Testing

Planned
Lesson 12 min
25

Writing Basic Test Scripts

Planned
Lesson 12 min
26

Assignment: Automate API Test

Planned
Assignment 20 min
27

Quiz: Automation Basics

Planned
Lesson 10 min

Module 6: Tool Agnosticism Locked

5 lessons · 58 min
28

CLI vs GUI Philosophy

Planned
Lesson 8 min
29

cURL Fundamentals

Planned
Lesson 10 min
30

Comparing Tools (Postman vs CLI)

Planned
Lesson 10 min
31

Assignment: Solve Same Task in 2 Tools

Planned
Assignment 20 min
32

Final Reflection

Planned
Lesson 10 min

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