GuideTechnology
10 min read
Prepare for backend interviews by concept: SQL joins, indexes and transactions, REST design, dependency injection and Spring Boot, JPA problems such as N+1 and lazy loading, security, testing, and a final job-ready checklist you can use to verify your own readiness.
GuideTechnology
10 min read
Prepare for Java interviews by concept: for each topic a short answer, the real explanation, a small example, the usual follow-up question and the common incorrect answer, covering the language, collections, streams, the JVM and concurrency.
GuideTechnology
8 min read
Put the whole backend together: the final architecture, the requirements checklist, how each article contributed, how to build, run and test it, an honest list of limitations, and the questions an interviewer is likely to ask about it.
GuideTechnology
9 min read
Prepare the Job Application Tracker to run outside your laptop: configuration and secrets from the environment, useful logging, Actuator health checks verified on the running application, a multi-stage Dockerfile and a Compose file, and a production checklist. The Docker files are written but were not run in this environment.
GuideTechnology
12 min read
Turn the tests from the earlier articles into a strategy: unit tests, slice tests (@WebMvcTest, @DataJpaTest, @JsonTest), full integration tests on a real PostgreSQL, measured run times, coverage with JaCoCo, and a mutation experiment that shows which tests really protect you.
GuideTechnology
46 min read
Secure the Job Application Tracker API: hash passwords with bcrypt, log in with signed JWT access tokens, enforce that users can only reach their own data, configure CORS and CSRF correctly, keep secrets out of the code, and prove each protection with tests and real requests.
GuideTechnology
35 min read
Add interviews to job applications and meet the real problems of JPA: relationship mapping, lazy loading and its exception, the N+1 query problem measured and fixed, what @Transactional does and does not do, and optimistic locking that stops lost updates, all tested on PostgreSQL.
GuideTechnology
29 min read
Replace the in-memory repository with a real PostgreSQL database using JPA, Hibernate and Spring Data: map an entity, manage the schema with Flyway migrations, understand the persistence context and dirty checking, write queries, and read the SQL Hibernate actually generates, including a real failure only PostgreSQL revealed.
GuideTechnology
30 min read
Build the first version of the Job Application Tracker API: a layered Spring Boot application with controller, service, repository, request and response DTOs, Bean Validation, paging and filtering, problem-details errors and tests, then exercise every endpoint over real HTTP.
GuideTechnology
15 min read
Learn what Spring Boot adds to Spring: the project structure, starters, auto-configuration and how it backs off, the embedded server, typed configuration with validation, profiles and the order in which configuration sources win, all run on a real Spring Boot 4.1 application.
GuideTechnology
18 min read
Understand dependency injection and inversion of control from first principles: wire objects by hand, build a tiny container, then see the real Spring container create beans, resolve ambiguity, manage scopes and lifecycle, and fail with the errors you will actually meet.
GuideTechnology
20 min read
Understand what actually travels between a client and a Java backend: the HTTP request and response, methods and their guarantees, status codes, headers, JSON and how Java maps to it, and how to design a clean REST API, with real captured traffic and real JSON mapping.
GuideTechnology
30 min read
Take the Expense Tracker CLI and add a PostgreSQL repository behind the same interface: an idempotent schema, a transactional bulk import, a connection pool, one shared contract test for every implementation, a fat jar, and an honest review.
GuideTechnology
25 min read
Learn JDBC, the standard way Java programs use a relational database: connecting with a driver, running queries with PreparedStatement, mapping rows, preventing SQL injection, transactions, error codes, batching and connection pooling, with every program run against PostgreSQL 18.
GuideTechnology
21 min read
Learn the SQL that backend developers use every day on PostgreSQL: tables and constraints, inserting, querying, joining and grouping data, transactions and isolation, indexes and query plans, and normalisation, with every statement run on a real PostgreSQL server.
GuideTechnology
29 min read
Build your first complete Java application: a command-line expense tracker with a clear design, money handled correctly, a file-based repository behind an interface, automated tests, a Maven build, and a runnable jar, then review it honestly.
GuideTechnology
16 min read
Learn to write reliable unit tests in Java with JUnit: structure, assertions, exception and parameterised tests, test lifecycle, then test doubles and Mockito, and the honest limits of mocking, all run in a real Maven project.
GuideTechnology
11 min read
A practical Git workflow for Java developers: the three areas, commits and good messages, branches, merging and resolving conflicts, pull requests, a correct .gitignore for Maven projects, and what to do when a secret is committed.
