Sebastian Sastre

Senior Software Engineer with a background at Telna, Sulvo, StarterSquad, Airflowing and a 5-star rating on Codementor. +55 (45) 98421-2515 Website | Blog | LinkedIn | GitHub

Work Experience

  • Senior Software Engineer

    Telna, Sep 2019 - Aug 2023
    • Joined a team of 6 as a Senior Software Engineer to keep the 12 engineers operations team and 50 member customer success teams running and escalating the main component of the roaming software. This resulted in 2022 driving 1 Petabyte of network traffic in the mobile north-american telecommunications market.
    • In 6 months I've refactored the main backend code to improve Separations of Concerns issues that were a blocker for containerization of the service. As a result of that, continuous deployment and automated scaling and improved monitoring became possible.
    • In 2 days, implemented a proof of concept to prove we could migrate from Voyage to Mapless to introduce significant improvements in the backend. After demonstrating this PoC to the Principal Telecommunications Architect and CTO and getting them impressed, it got approved and fully implemented in 3 months for 2 out of 3 protocols. That year I've got promoted to Senior Software Engineer and the service continued to grow.
    • Made and demonstrated a Rust caching system to extend the this microservice capacity which is currently above 25Kops and growing. Although this application is not in production at this time, its discoveries allowed other caching improvements increasing system capacity by alleviating significantly the DB usage.
    • Made a Golang multithreaded client to produce synthetic network traffic for stress testing the backend making possible to discover a virtual machine issue that the open source community and external consultants are resolving and the safe limits of each instance in operation.
    Smalltalk, Rust, Golang, Python, bash, TDD, Docker, SvelteKit, NextJs, Tailwind
  • Lead Software Engineer

    Sulvo, May 2017 - Dec 2018
    • As the team lead at Sulvo, working directly with the founder, I was responsible for designing and implementing the next generation ad server in a JavaScript-based stack. I collaborated with a team of five software engineers to ensure a smooth transition from the old system to the new one. I designed and implemented the operations for the new ad server and successfully migrated it from AWS to GCloud without any service disruption. In addition to my technical contributions, I also helped the founder hire three new engineers and led the team to migrate back from GCloud to AWS without any loss of data or functionality, despite handling billions of transactions globally. My leadership and technical expertise helped Sulvo establish a next-generation ad server with seamless migration between cloud platforms and a skilled team to support and enhance it.
    AWS, GCloud, JavaScript, Meteor, VueJS, NodeJS, MongoDB, Docker, Machine Learning
  • Full-stack Software Engineer

    StartedSquad, Apr 2015 - May 2016
    • In just one week, using Meteor, I developed an MVP for two founders of a dairy industry startup in the Netherlands. The MVP was designed to solve matching online demand and offer of cows in the dairy industry, and as a result of its success, later the founders were able to secure a Series A funding of €4M.
    • As a full-stack developer, I successfully developed and published a Swift native app in the App Store for a client. Additionally, I developed the app's NodeJS backend and Vue dashboard frontend, creating a complete solution that helped the client offer a seamless experience to his customers.
    • As a frontend developer, I joined 4 teams ranging from 2 to 12 developers, working on tasks using AngularJS and ReactJS. Notably, I mentored junior developers from in using AngularJS to develop new features for their platform in the energy sector. Additionally, I worked with cross-functional teams to complete frontend tasks using both AngularJS and ReactJS, ultimately improving the user experience and completing tasks weekly in a timely and efficient manner.
    Swift, ReactJS, Meteor, CircleCI, AngularJs
  • Flowing

    Jul 2009
    • Airflowing Small ad agencies had no system other than email and excel to keep the company organized in these days. After demonstrating an MVP to 8 ad agencies owners of the local commerce group (ACIFI), Airflowing was developed into a full software as a service (SaaS) product for end-to-end team management focused on medium/small businesses. It was designed to scale horizontally in the cloud in the days before the cloud was called the cloud. Airflowing helped clients to take control of sales, operations and cashflow. In its launch it received praise from Guy Kawasaki, Seth Godin and Derek Sivers Airflowing’s own clients.
    Smalltalk, Seaside, Object Oriented Database, jQuery, Marketing, UX/UI Design, Product Design, Business Development, MongoDB, Proprietary Frameworks, Public Speaking
  • Galenial Startup

    Nov 2007 - Nov 2008
    • After seeing physicians operating small clinics and organizing them with docs on Word and Excel, found experimenting the market potential by developing an MVP. Galenial was a product to aid in the administration of small clinics and medical practice management developed using Dolphin Smalltalk. Learned how to implement probabilistic search based on a Berkeley's paper (Cheshire II) and the process to deploy a full client-server product in Windows for two clinics.
    Smalltalk, Crystal Reports, Object Oriented Database, Non-boolean search
  • Independent consultant

    Feb 2003 - Dec 2005
    • Designed and implemented a Windows based desktop e-commerce application for Cromosol S.A. the Argentina's market leader of auto parts aftermarket in 2 months. This application successfully expanded all their distribution channels cross country and made ordering over fax obsolete.
    Smalltalk, Crystal Reports, Object Oriented Database, MySQL, PostgresSQL
  • Project Leader

    TEING Nov 1998 - Dec 2000
    • In my first job, joined a team of 4 software engineers to develop the next-gen client-server toll system using Dolphin Smalltalk and PostgreSQL to replace the old inflexible PLC-based system. Promoted to Project Leader after successfully installing the first version of the developed system in production.
    Smalltalk, Crystal Reports, PostgresSQL, Proprietary Hardware

Computer Languages

  • Smalltalk.
  • JavaScript.
  • Swift.
  • Rust.
  • Golang.
  • Python.


  • Fluent english.
  • Fluent portuguese.
  • Native spanish.

What are the engineering challenges your team is currently tackling?