API

Backend Concepts in Depth

Tokens, authorization, roles, middleware, sessions, cookies, exceptions, REST, GraphQL, cURL, Swagger, service container, Docker, queues, batches, cron, eager loading and Kafka, explained with banking, e-commerce and payment examples in Laravel, Spring Boot, React and MySQL.

10 topics62 questions & lessons

Tokens, Authentication, Authorization & Roles

7 sections · Open → 02

Middleware, Filters & Interceptors

5 sections · Open → 03

Sessions & Cookies

5 sections · Open → 04

Exception Handling

5 sections · Open → 05

REST APIs, GraphQL, cURL & Swagger

7 sections · Open → 06

Service Container, Service Providers, Dependency Injection & Annotations

6 sections · Open → 07

Docker for Laravel, Spring Boot, React, MySQL & Kafka

6 sections · Open → 08

Queues, Batches, Cron Jobs & Job Scheduling

7 sections · Open → 09

Slow Pages, Large Requests & Eager Loading (N+1)

6 sections · Open → 10

Events & Kafka in Banking, E-commerce and Payments

8 sections · Open →

Topics

Optional study guide

See the big picture · Backend Concepts in Depth

One request through a production backend

Start with the diagram, compare the concepts, then apply them to the lesson.

IdentitySession cookie or token authenticates the caller.
MiddlewareRate limits, request id and CSRF wrap the request.
Controller + policyValidate input, authorize the record, call a service.
Async workQueue jobs and publish events for everything the user need not wait for.

At a glance
Concept	Where it shows up
Tokens and roles	Net banking login, merchant API keys
Queues and batches	Order emails, monthly statements
Eager loading and pagination	Order history, transaction statements
Kafka events	Payment captured to settlement, fraud and notifications

Watch for this: Hiding a button in React is not authorization: the API must check identity, permission and ownership on every request.