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HTTP, JSON & API fundamentals

Understand HTTP exchanges and build deterministic URL, JSON, pagination and retry-policy tools over supplied offline responses.

Free lessons & exercises7 authored lessons2 units
Open the first lesson →Open the interactive course map

What you’ll work toward

Inspect request/response records, interpret methods and statuses, encode URL components, validate JSON pages and evaluate bounded client policies without making network requests.

Read an explanation, inspect the diagrams and work through the available checks, debugging exercises and builds. Feedback and prerequisite links guide the next step.

Before you start

This course builds on these skills:

Individual lessons can add prerequisites. The course map shows your actual readiness.

A look inside the first lesson

Requests, responses & transport failures

Python 
exchange = {
    "request": {"method": "GET", "target": "/books?tag=python"},
    "response": {"status": 404, "body": b""},
}
response = exchange["response"]
print(response is None)              # False: a response exists
print(response["status"], len(response["body"]))  # 404 0

Your course outline

Follow the lessons in curriculum order. Open a unit to preview the ideas you’ll work with.

UNIT 014 lessons HTTP messages and representation boundaries
  1. LESSON 01.01

    Requests, responses & transport failures

    Separate the request, HTTP response and absence of a response while inspecting honest offline exchanges.

    Open lesson
  2. LESSON 01.02

    Methods, status codes & retry meaning

    Distinguish safe and idempotent methods, status families and responses that carry no content.

    Open lesson
  3. LESSON 01.03

    Header names, values & content types

    Look up case-insensitive header names without corrupting values or pretending every repeated field can be merged.

    Open lesson
  4. LESSON 01.04

    URLs, path segments & query encoding

    Encode raw path segments and ordered query pairs without losing delimiters, repeats or blank values.

    Open lesson
UNIT 023 lessons Validated API data and bounded client policy
  1. LESSON 02.01

    JSON decoding, schemas & explicit errors

    Process status, content type, UTF-8, JSON syntax and API shape in a deliberate order without hiding failures.

    Open lesson
  2. LESSON 02.02

    Pagination, opaque cursors & termination

    Traverse supplied pages in server-declared order with cycle detection, explicit limits and no silent partial results.

    Open lesson
  3. LESSON 02.03

    Capstone: a deterministic API client policy

    Combine response validation with bounded retries, timeout decisions and Retry-After budgets over supplied offline attempt traces.

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