Every app you use has a part you can see and a part you cannot. The part you cannot see is the backend: it holds the data, decides what is allowed, does the arithmetic that matters, and answers questions over the network. This track is about becoming the person who builds that.
It is a roadmap, not a reference. Ten posts, each one topic, in the order the topics actually become useful. Read it once end to end and you will know what you need to learn, why each piece exists, and which of the deeper tracks on this site to go and read next.
Who this is for
- You can write some code and you want to know what a backend job actually consists of.
- You are self-taught and suspect there are large gaps — there are, and this names them.
- You have been doing frontend work and want to move across.
- You are about to interview and want the shape of the whole thing, not one framework's API.
You need to be able to write and run a program in some language. Nothing else is assumed.
What a backend actually does
Strip away the vocabulary and a backend is a loop. Something arrives over the network, you decide whether it is allowed, you read or change some stored data, and you send an answer back.
Here is one real request from the app this track uses — a customer placing a pizza order:
| Step | What happens | Post |
|---|---|---|
| 1 | POST /api/orders arrives with a JSON body | 5 |
| 2 | The security filter decides whether this caller may do this | 7 |
| 3 | The body is parsed and validated — is the quantity a positive number? | 5 |
| 4 | Prices are read from the database, never from the request | 6 |
| 5 | The order and its line items are written in one transaction | 6 |
| 6 | The confirmation email is pushed onto another thread so the caller is not kept waiting | 8 |
| 7 | 201 Created goes back with the order | 5 |
| 8 | A log line and a timing metric are recorded in case this is slow at 3am | 10 |
Every post in this track is one of those steps, or the thing that makes the steps possible.
The ten posts
- Get Started — this one.
- What a Backend Engineer Actually Does — the job, and where the line sits between you and everyone else.
- The Java and the JVM You Actually Need — the subset of the language that matters here, which is not the subset a beginner course teaches.
- What to Learn in a Framework — the small part of a big framework you use every day.
- HTTP and API Design — the contract you hand to every other team.
- Databases — schemas, indexes, transactions, and the mistakes that only show up under load.
- Authentication, Authorization and Security — who are you, and are you allowed to do that.
- Caching, Async Work and Messaging — three ways to stop making the caller wait.
- Testing — how you change code you did not write without being afraid.
- Deployment and Observability — getting it running somewhere real, and knowing when it breaks.
Read them in order the first time. After that each stands alone.
The stack every example uses
The concepts here are not Java concepts. An index, a cache, a JWT and an idempotent
PUT mean the same thing in Python, Go or C#. But examples have to be written in
something, and every example here is Java.
| What | Version |
|---|---|
| Java | 21 |
| Spring Boot | 4.1.0 |
| Jakarta EE | 11 — jakarta.*, never javax.* |
| JUnit | 6.0.3 (Jupiter) — the version Boot 4.1 ships. The
package is still org.junit.jupiter.api, so the annotations are unchanged. |
| Database | MySQL |
If you work in another language, read the prose and skim the code. The prose is the part that transfers.
Where the code comes from
Every snippet in this track is lifted from one real application: a pizza ordering API with a menu, a cart, guest checkout, Stripe payments, JWT authentication, an admin back office and reporting. Around 130 classes, backed by a test suite that runs green.
That constraint is deliberate. Invented snippets can demonstrate an annotation without ever having been compiled, and they never show the awkward parts — the comment explaining why the obvious approach was wrong, the guard added after something broke in production. Those comments are the most valuable thing in a real codebase and you cannot invent them.
Where this track stops and the others start
This track answers what do I need to learn and why. It does not try to be the last thing you read on any of these topics — each one has a deeper track here already:
| When you want | Go to |
|---|---|
| The language, properly | Java and modern Java features |
| The framework, properly | Spring Boot — 35 posts |
| To be asked about Spring in an interview | Spring Study Guide |
SQL beyond SELECT | SQL — 42 posts |
| To run it in the cloud | AWS — 33 posts |
| To pass the algorithms round | Data Structures & Algorithms |
| To design a system on a whiteboard | System Design |
How to use this track
Do not read all ten and then start building. Read a post, then go and do the thing it describes in a project of your own, however small. The gap between recognising an idea and being able to use it only closes when you type it out and it does not work the first time.