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Lucas León

@lucasleon

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Senior software engineer specializing in backend systems, API design, and scalable architectures.

Spain

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What I'm looking for

I seek backend or platform roles where I can design scalable systems, lead technical architecture, and improve reliability.

I am a Senior Software Engineer with 8+ years of experience building backend systems, APIs, and scalable architectures using Java, Kotlin and Spring Boot. I have led design and implementation efforts across high-traffic platforms—delivering CDC/Kafka streaming solutions, SDK enhancements, and performance-driven features that reduced costs and improved reliability.

I focus on pragmatic engineering: benchmarking technologies, delivering PoCs, and operationalizing systems with CI/CD, Kubernetes, and observability to increase uptime and fault tolerance. My work has driven measurable improvements—faster testing, reduced waiting times, improved uptime, and significant reductions in manual effort.

Experience

Work history, roles, and key accomplishments

Senior Software Engineer

Masabi

Nov 2024 - Dec 2025 (1 year 1 month)

Evaluated CDC solutions and built Kafka-based streaming components (Ktor + Spring Boot) for a high-traffic transit ticketing platform, reducing infrastructure costs and enabling loyalty features that served millions of riders.

Kotlin Spring Boot Ktor Kafka AWS SDK Development Microservices

Senior Software Engineer

Royal Caribbean

Feb 2022 - Jun 2024 (2 years 4 months)

Architected and implemented crew-facing and onboard security systems with Spring Boot and Kotlin, cutting security screening wait times by 50% and improving guest health system uptime by 90%.

Kotlin Spring Boot Coroutines Redis Kafka Kubernetes GitOps Performance Testing

Senior Software Engineer

Exactuals

Jun 2021 - Feb 2022 (8 months)

Built Java Spring Boot services to manage royalties for 100k+ members and introduced Spring Cloud Contract and unit testing practices, reducing inter-service test times by 70% and manual testing by 30%.

Java Spring Boot Junit Mockito AWS S3 Step Functions

Software Engineer

Royal Caribbean

Oct 2020 - Jun 2021 (8 months)

Launched COVID-related temperature and PCR testing services on 30+ ships using Kotlin and Spring WebFlux/Boot, improving monitoring for 1,000+ users and accelerating test development time via JUnit and MockK.

Kotlin Webflux Spring Boot Junit MockK Microservices Docker CI CD

Software Engineer

Fandango

Mar 2020 - Aug 2020 (5 months)

Led a web redesign and developed the Fandango TV feature using Laravel, Blade, Vue and Yii, increasing internal traffic by 30% and reaching 900k+ moviegoers in Latin America.

Laravel Vue.Js Yii PHP Refactoring

Back-End Developer

Comunal

Feb 2019 - Mar 2020 (1 year 1 month)

Maintained and extended Spring Boot APIs for 100+ businesses, implemented unit testing and CI/CD with Jenkins, and introduced SonarQube, improving stability and code quality while reducing deployment times by 80%.

Spring Boot Java Junit Jenkins SonarQube PostgreSQL CI CD API Development

Technical Lead

Dotty

Jan 2018 - Jul 2018 (6 months)

Led implementation of an e-commerce server using Spring Boot and Postgres on Heroku, delivered REST API and integrations (Auth0, Easypost, MercadoPago) in six weeks, reducing front-end integration and logistics effort.

Spring Boot PostgreSQL Heroku Auth0 REST APIs Swagger

Back-End Developer

Culqi

Mar 2017 - Jan 2018 (10 months)

Implemented an OAuth2 server with Express.js and Passport, added asynchronous fraud rules and automated business approval, improving payment gateway performance by 30% and reducing manual verification by 45%.

OAUTH2 Passports Fraud Detection Performance Optimization