I'm Sergio Martin Rubio


I’m a Senior Software Engineer with 9+ years of experience designing scalable, cloud-native applications and event-driven architectures. I specialize in high-performance 🚀 systems, and I’m a developer who likes challenges and is never afraid of diving into new territories.

I’ve built software for Bitclear AG, Bound, RavenPack, Marshmallow, Expedia Group and Gamesys — from automated currency hedging and crypto payments to authentication infrastructure serving millions of users. While I have deep experience in the Java ecosystem, I also work extensively with TypeScript and JavaScript, building modern web applications and APIs. I love writing clean, modular, and maintainable code ✨.

I enjoy sharing what I learn and getting inspired by others — which is what this blog is for. I would be glad to help you! 😀 Contact me any time ✉️

My Expertise:

My expertise covers a wide range of technologies like Java 8+, Spring Boot, TypeScript, JavaScript, NestJS, ReactJS, Python, GraphQL, Kubernetes, AWS, GCP, PostgreSQL, MySQL, Docker, Git, Jenkins, and Grafana. I have extensive experience in designing scalable, event-driven architectures and following best practices for microservices, with a strong focus on TDD and continuous integration. Outside of backend work I also build native iOS apps with Swift and SwiftUI. Agile methodologies (Scrum, Kanban) are also part of my skill set.

Where I've Worked:

Software Engineer · Bitclear AG

Jun 2024 - Jun 2026

Contract · Remote

Backend engineer on a crypto fintech microservices platform, leading end-to-end delivery across the compliance, brokerage and payments domains. Led the EU Travel Rule compliance integration, designed a multi-asset liquidity planner that builds fee-optimized execution plans, and delivered a crypto-to-FIAT card payment integration that increased cashflow by 20%.

Java Spring Boot TypeScript NestJS PostgreSQL

Software Engineer · Bound

Oct 2021 - Jun 2023

Contract · Remote

Built new products and services from scratch alongside product managers, and integrated accounting, invoicing and banking services to bring customers one step closer to a fully automated currency hedging solution.

Java AWS

Java Developer · RavenPack

Dec 2020 - Sep 2021

Marbella, Spain

Worked on a microservices architecture and made architectural decisions. Migrated Java applications to serverless, and reviewed and reduced AWS operating costs.

Java Python AWS Lambda

Software Engineer · Marshmallow

Nov 2019 - Nov 2020

London, United Kingdom

Built back-office automation that reduced operational costs by 80%. Improved the authentication mechanism and shipped self-service features that cut customer support requests by 30%. Onboarded and mentored new engineers.

Java Spring Boot

Software Development Engineer · Expedia Group

Oct 2018 - Nov 2019

London, United Kingdom

Adapted microservices APIs to support new features, redesigned the caching architecture around in-memory data structures, and ran a GraphQL proof of concept.

Java ReactJS GraphQL

Software Engineer · Gamesys

Oct 2017 - Oct 2018

London, United Kingdom

Redesigned the authentication and authorization infrastructure to handle millions of users. Practised TDD and pair programming daily, and maintained the Kubernetes cluster and CI tooling across the department.

Java Spring Security Kubernetes

Full Stack Developer Intern · Accenture

Mar 2017 - Sep 2017

Málaga, Spain

Designed and implemented new features with Java EE technologies, and built a Go service that used Spring Batch to rehash and process millions of records.

Java EE Go AngularJS

Projects I've Worked on:

All Projects

Articles I've Written:

All Articles

I started this blog to become a better software engineer and stay up to date with the latest practices and technologies. 🤓

I began learning Java in 2017 and read many amazing books 📚 at the start, such as Effective Java, Java 8 in Action, and TCP/IP Sockets in Java. However, after a year, I realized that simply reading these books without hands-on practice wasn't the best use of my time. 😞 That's when I decided to create my personal tech blog to document and solidify what I learn outside of work. 💡 😃

Over time, this blog has grown beyond just Java and software engineering fundamentals. I now write about a variety of topics, from backend development, cloud computing, and DevOps to blockchain, smart contracts, and modern web technologies. Sharing my experiences not only helps me deepen my understanding but also allows me to contribute back to the tech community.

Whether it's breaking down complex concepts, exploring best practices, or experimenting with new tools, this blog is my personal space for continuous learning and sharing knowledge. 🚀

Recommendations:

7 recommendations from managers and colleagues on LinkedIn.

Piotr KucharskiProviding software that will boost your businessJune 2026 I had the pleasure of working with Sergio on our engineering team. What stood out most was his work ethic and reliability. Sergio consistently show... Read more Show less

I had the pleasure of working with Sergio on our engineering team. What stood out most was his work ethic and reliability. Sergio consistently showed up prepared, met his commitments, and was always approachable and easy to collaborate with — qualities that always appreciated and especially in technical environments. He does his best work in structured settings with well-defined scope, where his diligence and attention to detail can really shine. I wish Sergio well in his next role and am confident he'll be a dependable member of any team.

Dan KindlerFounder at Bound | Currency hedging on cruise controlJuly 2023 Working with Sergio in his capacity as a senior engineer has been an incredibly delightful experience. I can confidently affirm his exceptional tec... Read more Show less

Working with Sergio in his capacity as a senior engineer has been an incredibly delightful experience. I can confidently affirm his exceptional technical knowledge and problem-solving capabilities. Sergio possesses extensive expertise in Java and microservices architecture, and his knack for discovering innovative solutions to intricate issues has proven to be an invaluable asset to Bound. Sergio excels in leading collaborative projects with fellow team members and consistently delivers outcomes within designated timeframes. His remarkable talent lies in effectively conveying technical information and collaborating seamlessly with non-technical colleagues. Sergio led the development of a project that became one of Bound’s most profitable products, highlighting both his technical prowess and exceptional interpersonal abilities.

Gonzalo BahutDirector of EngineeringOctober 2021 During the time Sergio worked for Ravenpack, he showed a great professionalism and excellent attitude. Sergio is a fast learner and a competent eng... Read more Show less

During the time Sergio worked for Ravenpack, he showed a great professionalism and excellent attitude. Sergio is a fast learner and a competent engineer with a will to deliver high quality code in time. In addition to his technical qualities, Sergio demonstrated good social and teamwork skills.

Hanson ChowCTO @ Kneu Health | Building Regulated Health Tech | Backend & Platform EngineerNovember 2020 It was an absolute pleasure to work with Sergio for the past year. Sergio is one of the best teammates that you can find, as he always find time to... Read more Show less

It was an absolute pleasure to work with Sergio for the past year. Sergio is one of the best teammates that you can find, as he always find time to do what is necessary and do it right. Sergio always takes feedback on board as well and contributes to discussions constructively, which really helped us grow the engineering culture in our team. It's going to be difficult for us to find another Sergio!

Antonio MasucciHelping businesses design, build and scale AI systemsJuly 2018 “Smiling learner” that’s what comes to my mind when I think about Sergio. Sergio reported to me during my time at Gamesys as a software engineer an... Read more Show less

“Smiling learner” that’s what comes to my mind when I think about Sergio. Sergio reported to me during my time at Gamesys as a software engineer and he demonstrated to be a brilliant team player and a very capable engineer. He tackles the hardest problems and gives always 110%. I would recommend Sergio as an excellent software engineer to any company.

Mallory Rowan130K+ Digital Community | Speaker | Creator | Build without BurnoutMay 2015 Sergio played a major role in launching our digital analytics efforts. He has a great attention to detail and always provided exemplary reports. He... Read more Show less

Sergio played a major role in launching our digital analytics efforts. He has a great attention to detail and always provided exemplary reports. He is an independent worker with great initiative to tackle new projects, and a pleasure to work with.

Marty Krátký-KatzExited Tech FounderMay 2015 Sergio worked with us at MicroMetrics for 4 months, and it was a pleasure to oversee & manage his work; he brings a positive attitude to everything... Read more Show less

Sergio worked with us at MicroMetrics for 4 months, and it was a pleasure to oversee & manage his work; he brings a positive attitude to everything he does, and always showed great initiative in taking on new tasks & projects. He worked with us in a digital marketing role, conducting research on our competitors’ digital marketing efforts with the aim of shaping & guiding our own digital marketing strategy, as well as making recommendations relating to digital marketing best practices. In his role, he showed very strong market research skills, as well as proficiency with the typical computer & web competencies that were expected of the role. He always communicated very well with everybody on the team, and very capably led periodic briefing sessions to present his latest research findings. We often tasked him with research projects to take the lead on, and he always performed above & beyond expectations, showing great attention to detail, and enthusiasm for his work. He was a pleasure to work with, and I would be very happy to have him on the team again in the future!