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Java ProgrammingFrom objects and collections to lambdas, streams, concurrency and design patterns — the core Java skills every backend developer relies on.13 guides →Spring FrameworkDependency injection, bean configuration, AOP, data access, MVC, REST, security and testing — the Spring Framework explained from the ground up.10 guides →Spring Boot & Spring CloudBuild, configure, document, test and deploy production-ready services with Spring Boot, Spring Data, Spring Batch and Spring Cloud.11 guides →Java EE / Jakarta EEApplication servers, servlets, JSF, EJB, JMS, JPA, JTA, JAX-RS and XML processing — the enterprise Java platform and how its pieces fit together.10 guides →Messaging & Event StreamingJMS, ActiveMQ, RabbitMQ and Apache Kafka: message brokers, delivery guarantees, routing patterns and how to use them from Java.10 guides →DevOps, CI/CD & ContainersGit, Jenkins pipelines, continuous delivery, Docker, Kubernetes and infrastructure as code — the practices and tools that ship software reliably.14 guides →Linux AdministrationThe filesystem, the shell, users and permissions, processes and systemd, packages, networking, scripting, text processing and troubleshooting.10 guides →Software ArchitectureLayered systems, SOA, microservices, DDD, REST and API management, reactive systems, performance, TOGAF and distributed consistency.12 guides →Cloud ComputingCloud fundamentals, AWS and Azure core services, well-architected design, migration strategies, high availability, cloud-native apps and cost control.8 guides →Data & DatabasesSQL best practices, schema design, Oracle vs PostgreSQL, indexes and execution plans, MongoDB, Solr, the ELK stack, big data, Hadoop and BI.10 guides →Software Testing & QualityTesting fundamentals, JUnit and Mockito, TDD, BDD with Cucumber, integration and performance testing, automation strategy and static analysis.8 guides →Agile & Project ManagementAgile principles, Scrum roles and events, backlog management, estimation, scaling with SAFe, and classic project management: scope, schedule, cost, risk.11 guides →Security & IdentityApplication security architecture, OAuth 2.0, OpenID Connect, SAML and SSO, identity and access management, JWT-secured APIs and the OWASP Top 10.8 guides →Web & Mobile DevelopmentHTML5 essentials, JavaScript fundamentals, jQuery, Angular, migrating from AngularJS, Android basics and a complete HTTP status code reference.7 guides →Fintech & BankingHow payments, cards, PSD2 open banking, capital markets and financial markets work, plus blockchain fundamentals and Ethereum smart contracts.7 guides →
Featured guides
Jakarta EEJakarta Transactions (JTA 2): Container-Managed Transactions, Propagation and XAHow JTA transactions work in a Jakarta EE server: isolation, @Transactional propagation, rollback rules, UserTransaction and XA two-phase commit.Intermediate9 min readMessagingKafka Producers and Consumers in Java: Offsets, Idempotence and TransactionsKafka clients in Java: producer batching, acks and idempotence, the consumer poll loop, offset commits, rebalances, exactly-once transactions and Spring Kafka.Intermediate7 min readLinuxgrep, sed and awk: Text Processing Pipelines That Answer Real QuestionsRegular expressions, grep options, sed substitution and addressing, awk fields and patterns, plus cut, sort and uniq in log-analysis pipelines.Intermediate9 min readProject ManagementCost Management and Earned Value: A Worked EVM ExampleBudgeting, the cost baseline and earned value management explained with a full numeric example — PV, EV, AC, SPI, CPI, EAC, ETC, VAC and TCPI.Advanced7 min readSecurityOAuth 2.0 Explained: Roles, Grants, PKCE and Current Best PracticeHow OAuth 2.0 delegates authorization: roles, the authorization code flow with PKCE, client credentials, device flow, scopes and RFC 9700.Intermediate7 min readJavaJava Object-Oriented Basics: Classes, Objects, Fields and MethodsHow Java classes, objects, constructors, fields, methods, encapsulation, static members and records work, with the mental model behind references and the heap.Beginner9 min read