The Dev World - by Sergio Lema

The Dev World - by Sergio Lema Are you ready for a Dev Challenge? Welcome to The Dev World.

Professional developer since 2008, I'll share my knowledge with games and videos about the technologies I master: Java, databases, DevOps tools and more.

Why You Should Never Use Floating Point for MoneyThe floating-point arithmetic are inadequate for financial systems, adv...
01/06/2026

Why You Should Never Use Floating Point for Money

The floating-point arithmetic are inadequate for financial systems, advocating for the use of BigDecimal to ensure precision and avoid rounding errors. Key principles include domain isolation, stringent data types, and thorough edge-case testing. Proper implementation is crucial for maintaining price integrity and avoiding financial discrepancies....

The floating-point arithmetic are inadequate for financial systems, advocating for the use of BigDecimal to ensure precision and avoid rounding errors. Key principles include domain isolation, stri…

Optimizing Search Performance with CQRS: Relational Writes and NoSQL ReadsMost developers initially rely on relational d...
25/05/2026

Optimizing Search Performance with CQRS: Relational Writes and NoSQL Reads

Most developers initially rely on relational databases, but as search demands grow, performance declines. Command Query Responsibility Segregation (CQRS) effectively tackles this by separating read and write operations. The write side focuses on data integrity, while the read side prioritizes speed, often utilizing NoSQL stores for efficient retrieval and eventual consistency between systems....

Most developers initially rely on relational databases, but as search demands grow, performance declines. Command Query Responsibility Segregation (CQRS) effectively tackles this by separating read…

18/05/2026

Granular Authorization in Spring Boot: Beyond Role Checks

Most applications have robust authentication and brittle authorization. A single if (user.isAdmin()) block guarding critical data is not a security model — it's a liability. This post walks through the evolution from scattered role checks to a clean, declarative ABAC approach using Spring Security's PermissionEvaluator, RoleHierarchy, and SpEL....

Most applications have robust authentication and brittle authorization. A single if (user.isAdmin()) block guarding critical data is not a security model — it’s a liability. This post walks t…

Making Testcontainers Work with Lima on macOSIf you switched from Docker Desktop to Lima and Testcontainers started fail...
11/05/2026

Making Testcontainers Work with Lima on macOS

If you switched from Docker Desktop to Lima and Testcontainers started failing silently, here is the exact configuration you need — five steps, no guessing....

If you switched from Docker Desktop to Lima and Testcontainers started failing silently, here is the exact configuration you need — five steps, no guessing.

04/05/2026

Event-Driven Architecture with Spring Boot and AWS EventBridge: Escaping the Distributed Monolith

Most microservice migrations just trade a local monolith for a distributed one. This post covers how to implement Event-Driven Architecture with Spring Boot and AWS EventBridge — from choreography patterns and schema contracts to idempotency and distributed tracing....

Most microservice migrations just trade a local monolith for a distributed one. This post covers how to implement Event-Driven Architecture with Spring Boot and AWS EventBridge — from choreography …

Google Cloud Run Limitations: When Serverless Complexity Outweighs the Cost SavingsGoogle Cloud Run is a great fit for s...
27/04/2026

Google Cloud Run Limitations: When Serverless Complexity Outweighs the Cost Savings

Google Cloud Run is a great fit for simple APIs, but once you need large file uploads, high availability, and event-driven reliability, the workarounds pile up fast. This post walks through the real cost of fighting Cloud Run's constraints and when GKE Autopilot or Compute Engine becomes the more honest choice....

Google Cloud Run is a great fit for simple APIs, but once you need large file uploads, high availability, and event-driven reliability, the workarounds pile up fast. This post walks through the rea…

The Command Pattern in Java: Eliminating Fat Service Classes with Commands and HandlersFat Service classes are a liabili...
20/04/2026

The Command Pattern in Java: Eliminating Fat Service Classes with Commands and Handlers

Fat Service classes are a liability — one class that does everything is a class that's impossible to test and dangerous to change. This post shows how to apply the Command pattern in Java using Records, Repository interfaces, and single-responsibility Handlers to keep your business logic clean and isolated....

Fat Service classes are a liability — one class that does everything is a class that’s impossible to test and dangerous to change. This post shows how to apply the Command pattern in Java usi…

Spring Security 6 OAuth 2.1: Replacing Implicit Grant and ROPC with PKCEIf your Spring Security config still uses the Im...
13/04/2026

Spring Security 6 OAuth 2.1: Replacing Implicit Grant and ROPC with PKCE

If your Spring Security config still uses the Implicit Grant or Resource Owner Password flow, you're running on borrowed time. This post breaks down why OAuth 2.1 makes PKCE mandatory, kills legacy flows, and shows the exact config difference between a legacy setup and a production-hardened one....

If your Spring Security config still uses the Implicit Grant or Resource Owner Password flow, you’re running on borrowed time. This post breaks down why OAuth 2.1 makes PKCE mandatory, kills …

Why JavaScript Floating Point Math Breaks Your App (And How to Fix It)JavaScript's IEEE 754 floating point format means ...
06/04/2026

Why JavaScript Floating Point Math Breaks Your App (And How to Fix It)

JavaScript's IEEE 754 floating point format means 0.1 + 0.2 !== 0.3 — and that's just the obvious case. This post covers why it happens, where it silently breaks production code, and four concrete strategies: toFixed for display, integer arithmetic for money, a scale-round-ceil pattern for computed floats, and decimal.js for complex chains....

JavaScript’s IEEE 754 floating point format means 0.1 + 0.2 !== 0.3 — and that’s just the obvious case. This post covers why it happens, where it silently breaks production code, and fo…

After 15 years in this industry, I have developed a very low tolerance for "ceremony." If a project takes more than five...
30/03/2026

After 15 years in this industry, I have developed a very low tolerance for "ceremony." If a project takes more than five minutes to move from a git clone to a running development environment, it is poorly designed.

We often mistake complexity for sophistication. In reality, the most sophisticated stacks are those that disappear into the background, allowing you to actually write business logic. This post outlines the foundational setup for my Fullstack 2026 series, focusing on Spring Boot 3.4 and React 19. The goal is to eliminate boilerplate, automate infrastructure, and restore sanity to the development lifecycle.

After 15 years in the industry, the author emphasizes the need for simplicity in development. The post discusses using Spring Boot 3.4 and React 19 to streamline setups by eliminating boilerplate, …

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