Albert Callarisa, Cryptocurrency Developer in Castelldefels, Spain
Albert Callarisa

Cryptocurrency Developer in Castelldefels, Spain

Member since October 23, 2017
Albert is a very passionate software engineer with over a decade of experience. During his career, he's focused on mostly back-end development and scalability. He's helped many companies (in different stages) achieve stellar engineering results from startups laying down the foundation for a new engineering team and culture to already established companies with aggressive growth plans.
Albert is now available for hire




Castelldefels, Spain



Preferred Environment

Docker, Git, Visual Studio Code, MacOS

The most amazing...

...thing I've built was an API that served non-cached data in 3 milliseconds (95th percentile).


  • Senior Software Developer

    2017 - PRESENT
    • Deployed a testnet with miners, archive nodes, a web wallet, dashboard, and netstats using Kubernetes.
    • Built an app to monitor blockchain and notify users when they've received funds.
    Technologies: Ethereum, Cryptocurrency, Amazon, Kubernetes, Docker, Go
  • Software Engineer

    2017 - 2017
    Osmond Marketing (via Toptal)
    • Helped detect an issue related to a database connection pool.
    • Fixed the issue and refactored the code to make sure it doesn't happen again.
    Technologies: PostgreSQL, Koa, Node.js
  • Senior Software Engineer

    2015 - 2017
    Axiom Zen
    • Improved the performance and scalability of a high throughput consumer app.
    • Built APIs from scratch for multiple prototypes of internal project ideas.
    • Refactored the general architecture of a machine learning product to support horizontal scaling.
    • Collaborated with multiple non-technical colleagues to define and plan projects.
    • Gave support to other projects where I wasn't directly assigned.
    • Experimented with Unity and VR for a few prototypes.
    • Collaborated in the build of a custom API framework used to generate APIs for new prototypes in less time.
    Technologies: Amazon Web Services (AWS), AWS, Docker, MongoDB, Redis, PostgreSQL, Elixir, Node.js, Go
  • Senior Software Engineer

    2013 - 2014
    • Interviewed and built up the technical team.
    • Defined all the architecture of the application and ensured that the team followed that direction.
    • Established and maintained a good engineering culture.
    • Worked closely with the founders in order to define the product direction.
    • Built an API with a high number of writes and reads with very low response times using PostgreSQL as a single source and Redis with a denormalized view of the data for extremely fast reads.
    • Experimented with popular front-end technologies to define the web client architecture.
    • Supported the iOS developers so that they would be able to interact with the API in the most efficient way.
    Technologies: Amazon Web Services (AWS), AWS, RabbitMQ, Redis, PostgreSQL, Node.js
  • Senior Software Engineer

    2011 - 2013
    • Led a team of up to five people.
    • Defined and implemented some of the core microservices in the application.
    • Solved many scalability issues due to the high throughput of the API.
    • Improved the data synchronization among the multiple worldwide clusters—reducing the delay of data distribution to almost real-time.
    • Deployed and maintained my own microservices on AWS.
    • Implemented TDD and full-time pair programming which was the core of our company's culture.
    Technologies: Amazon Web Services (AWS), AWS, Redis, PostgreSQL, Node.js, GoLand, Go, Ruby on Rails (RoR), Ruby
  • Software Developer

    2007 - 2009
    • Built an open source CMS to be able to ship new projects in less time for future clients.
    • Worked closely with some clients to understand their needs and design a good solution.
    • Defined the interface of those CMS modules and how they connected all together with the core of the CMS.
    • Documented on how to use the CMS from the developer's point of view with guides and videos. Also helped the rest of the team in using that CMS.
    • Aided in the build of a very complex video manipulation application, using mostly FFmpeg in the background to perform tasks.
    Technologies: PostgreSQL, Ruby on Rails (RoR), Ruby


  • Toby

    During my time at Axiom Zen, I worked on Toby: a tab management extension for Google Chrome. I rewrote the back-end to allow users to sync their data across browsers and also added team and individual tabs for sharing.
    Technology Stack: Go, PostgreSQL

  • ZenHub

    During my time at Axiom Zen, I contributed to ZenHub: a project management tool on top of GitHub. I improved the back-end and extended it with new features.
    Technology Stack: Node.js, MongoDB

  • Routific

    During my time at AxiomZen, I worked on Routific: a route optimization service. I helped maintain and improve the back-end of the service.
    Technology Stack: Node.js, Lisp

  • Unfollow Notification

    A simple service that notifies Twitter users when they get unfollowed. The main difference between this service and the rest is that I used the Twitter DM to communicate with the user so the user doesn't have to leave Twitter.

    It was an interesting project because it had to handle so many API requests to the Twitter API and the usage limits are very low.

  • WeAreBash

    During my time at Axiom Zen, I developed a virtual reality (VR) project called Bash. It's a VR experience where users watch live streams with their friends in virtual reality. I built the back-end API (Go, PostgreSQL), the video-streaming platform (migrating WebRTC to HLS), and the VR app (Unity) as well as the automation of the deployment of all the pieces.


    This is a background job runner based on Docker containers where each task runs in a volatile container.

    When I was building this product, serverless services like AWS lambda didn't exist and similar products had a very limited way for me to integrate with them. I engineered a really flexible solution so that it could be run any language, even Bash scripts, in a background job kind of system (with queues, workers, and the like).

    Today there are lots of alternatives and this product is not very useful so I decided to open source it. It was a challenging problem to solve considering the technology available at that time.


  • Languages

    JavaScript, Go, Ruby, SQL, Elixir, C#
  • Libraries/APIs

  • Tools

    Travis CI, Jenkins, RabbitMQ, Git, GoLand, CircleCI
  • Frameworks

    Express.js, Koa, Ruby on Rails (RoR)
  • Paradigms

    Test-driven Development (TDD), Behavior-driven Development (BDD), Functional Programming, Agile Software Development
  • Platforms

    Kubernetes, Docker, MacOS, Visual Studio Code, Amazon, Amazon Web Services (AWS), Ethereum
  • Storage

    Redis, PostgreSQL, MongoDB, NoSQL
  • Other

    AWS, Cryptocurrency, HTC Vive


  • Bachelor's Degree in Computer Science
    2005 - 2008
    Universitat Politècnica de Barcelona - Barcelona, Spain

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