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Every course, by domain

35 courses across 12 domains. 208 lessons are written; 35 more are outlined on their course pages so you can see what is coming. Start anywhere — the roadmap suggests an order.

Core Java

The language, properly: types, objects, collections, generics, and everything Java 8 through 25 added.

Foundation
Java Fundamentals
The language as the JVM sees it.
16 lessons~3h
Foundation
Programming Foundations
Before the language, the machine and the craft.
15 lessons~3h
Foundation
Setting Up Java
Install it, run it by hand, understand what you installed.
8 lessons~1h
Foundation
Object-Oriented Java
Objects as a design tool, not a syntax.
9 lessons~2h
Foundation
Collections and Generics
Pick the right structure; know what it costs.
9 lessons~2h
Intermediate
Modern Java: 8 to 25
The Java that is written today.
14 lessons~3h
Intermediate
Exceptions, I/O and Reflection
The parts of the standard library a backend leans on.
6 lessons~1h
Intermediate
Data Structures and Algorithms in Java
Enough to pass an interview, and enough to pick the right collection.
11 lessons~2h

Advanced Java

Concurrency you can reason about, and a JVM you can read: memory model, garbage collection, class loading, profiling.

Advanced
Java Concurrency
Correct first. Then fast.
9 lessons~2h
Advanced
JVM Internals and Performance
Read the machine your code runs on.
6 lessons~1h

Spring

Spring Core, Boot, Data JPA and Security — the framework as it is used in production, not as it is demoed.

Intermediate
Spring Core
The container, understood.
4 lessons~1h
Intermediate
Spring Boot
Auto-configuration, and what it decided for you.
5 lessons~1h
Intermediate
Spring Data JPA and Hibernate
The ORM, without the surprises.
5 lessons~1h
Advanced
Spring Security
The filter chain, and what it protects.
4 lessons~1h

API Engineering

REST that survives contact with clients: design, validation, errors, pagination, versioning, idempotency, rate limits.

Intermediate
REST API Engineering
An API is a contract other people build on.
8 lessons · 1 outlined~2h
Advanced
GraphQL and gRPC
When REST is the wrong shape.
0 lessons · 2 outlined~1h

Databases & Data

Relational databases in depth, then MongoDB, Redis and search — indexes, transactions, isolation, locking, replication.

Intermediate
Relational Databases in Depth
SQL, then what the engine does with it.
15 lessons~3h
Intermediate
MongoDB
Document modelling and where it pays off.
0 lessons · 3 outlined~1h
Intermediate
Redis and Caching
Fast, until it is wrong.
4 lessons~1h
Advanced
Search with Elasticsearch
Relevance is a feature, not a query.
0 lessons · 3 outlined~1h

Microservices

Service boundaries, discovery, gateways, resilience, and the data problems distribution creates: sagas, outbox, CQRS.

Advanced
Microservices Architecture
Boundaries first. Then everything that goes wrong across them.
7 lessons~2h
Senior
Distributed Data Patterns
The transaction you no longer have.
0 lessons · 3 outlined~1h

Messaging

Kafka as a system: partitions, consumer groups, rebalancing, offsets, retries, dead letters, schema evolution, exactly-once.

Advanced
Apache Kafka
A log, and everything that follows from it.
8 lessons~2h

DevOps & Cloud

Git, Maven and Gradle, Docker, Kubernetes, CI/CD, Linux, Nginx, and AWS — the path from a commit to a running service.

Foundation
Git, Maven and Gradle
The tools between your editor and the artifact.
3 lessons~1h
Intermediate
Docker
Your service as an artifact.
0 lessons · 3 outlined~1h
Advanced
Kubernetes
Declare the state; let the controllers chase it.
0 lessons · 3 outlined~1h
Intermediate
CI/CD, Linux and Nginx
From commit to running, repeatably.
0 lessons · 4 outlined~1h
Intermediate
AWS for Backend Engineers
The services a Java backend actually runs on.
0 lessons · 3 outlined~1h

Testing

JUnit 5, Mockito, Testcontainers, contract and performance testing — tests that catch the bugs that ship.

Intermediate
Testing Java Services
Tests that catch the bugs that ship.
3 lessons · 4 outlined~1h

Observability & Production

Logs, metrics, traces, and the discipline of diagnosing a live system: incidents, RCA, memory leaks, slow queries.

Advanced
Observability
Logs, metrics, traces — and the questions they answer.
5 lessons~1h
Senior
Production Engineering
The incidents, and the method that resolves them.
13 lessons~3h

Security

Authentication, authorization, JWT, OAuth2, OWASP, secrets — the parts a backend engineer is personally responsible for.

Intermediate
Application Security
The parts you are personally responsible for.
7 lessons~1h

System Design

High-level design, low-level design and distributed systems: capacity, trade-offs, failure handling, and how to argue them.

Advanced
System Design Fundamentals
Estimate, decide, defend.
9 lessons~2h
Intermediate
Low-Level Design
Classes, interfaces and the reasons for them.
3 lessons · 3 outlined~1h
Senior
Distributed Systems
What can go wrong will, in an order you did not expect.
2 lessons · 3 outlined~1h