Résumé

Hi, my name is Dan Zajdband. I’m a software engineer based in Madrid. I’ve been building software for close to twenty years, the last ten of them in fintech: payment infrastructure, digital banking and, currently, charitable giving. Most of my work is the ordinary engineering behind moving money safely, designing services and APIs, getting the edge cases right, and shipping products people trust with their savings.

I work across the stack with a strong back end bias: services, money movement flows, APIs, and the teams that build them. Some of what I ship these days uses LLMs, mostly for search, entity resolution and product features. It’s one tool in the box rather than the job itself. I was part of the initial team behind Next.js and I’ve been contributing to open source for over fifteen years. I also co-created BAFrontend, one of the top web technology meetups in Argentina, and I’m part of the JSConf Argentina organization team. Earlier in my career I spent several years building tools for newsrooms and experimenting with WebVR; that work is still further down this page.

Experience

  • Founding team Engineer – Daffy (2021 – present): Daffy is a donor-advised fund: members set money aside for charity, invest it, and give it away, for a flat monthly fee instead of a percentage. I joined as part of the founding team and work end to end: back end services and money movement (contributions in cash, stocks, ETFs, mutual funds and 300+ crypto assets), search and entity resolution over the ~1.7M IRS-qualified charities, the investment side, and the web and iOS products that families and financial advisors share. Part of that work now involves building AI-based features on top of all of it.
  • Senior Software Engineer – Accel Robotics (2019 – 2021): Autonomous retail powered by computer vision. I built the software behind checkout-free stores, working close to the machine learning pipeline that turns camera feeds into transactions.
  • Back End Team Lead – Brubank (2017 – 2019): Argentina’s first fully digital bank. I led and managed the Back End team, building and scaling the core banking services behind the app.
  • Lead Front End Developer – Mango (2013 – 2015): Online payment solution for developers and businesses in Latin America, bought by Mercado Libre in 2016. A small team, so I worked on a bit of everything, back end included: I created and maintained the customers control panel, and wrote the JavaScript SDK and the developer libraries.
  • Knight-Mozilla Fellow – Coral Project (Mozilla / New York Times / Washington Post) (2016 – 2017): A year of full-time open source work on community and publishing tools, plus research on emerging web platforms.
  • IT advisor – Chequeado (2012 – present): Argentinian fact-checking organization. I advise on technology decisions and help build their tools and data projects.
  • Senior Developer – theLIFT (2012 – 2013): Digital innovation agency based in San Diego, CA. I worked with startups and large companies like Sony and Qualcomm, and on the Zappos Pop-Up Shop with OrderWithMe.
  • Senior Developer – Vulsai (2011 – 2012): Digital creative studio in Buenos Aires. I built applications for Disney and Univision while contributing to open source.
  • Co-founder – Gravity On Mars (2009 – 2011): A studio building open source projects for the community and for companies.
  • Freelance Developer (2007 – 2013): Back End and Front End web development.

Projects

The things I built, with a team and on my own, are on the homepage, drawn in ink: HackDash, Guri VR, Tuiter, Gambeta, Tiny Replay and the rest, with links to what others wrote about them.

Skills

AI

  • LLM APIs and agents (OpenAI, Anthropic), tool calling
  • Embeddings, vector search and retrieval
  • Product features built on top of LLMs, end to end
  • Evaluation harnesses, prompt iteration, cost and latency tuning

Fintech

  • Payments and money movement flows
  • Banking, brokerage and custody integrations
  • High-availability back end services in regulated environments
  • Leading and growing back end teams

Languages and platforms

  • TypeScript / JavaScript (Node.js, React, Next.js)
  • Python
  • Go
  • PHP, C, C++
  • Web technologies (CSS, HTML)

Databases and infrastructure

  • PostgreSQL
  • MySQL
  • Redis
  • MongoDB
  • Serverless and static deployments

Talks

Books and courses

In the media

Education

  • University of Buenos Aires – B.Sc. Computer Science Candidate (Relevant coursework: Statistics, Algorithms, Operating Systems, Natural Language Processing)

Contact