Santiago Mansilla .

About

Hi, I'm Santiago.

I'm a Senior Software Engineer based in Valencia, Spain, with 8+ years across fullstack engineering — frontend-leaning, backend-comfortable, architecture-obsessed. I currently work at Sesame HR, where I lead the migration of the finance vertical to Vue 3 and build AI-assisted tooling for HR workflows.

Before Sesame, I was Tech Lead at Corporalabs (digital showroom & e-commerce), grew the engineering team at Horizm from 3 to 15+, helped migrate Hello Prêt's mortgage broker UI from PHP templates to Vue, and started my career at DynamicBrain leading frontend in a digital marketing agency.

I write here about frontend architecture, Vue migrations, Clean Architecture in real-world frontend codebases, and what changes when AI tooling lands in a serious engineering team. The signal-to-hype ratio is high. I leave the hot takes for Twitter.

What I care about

  • Explicit dependencies. If your domain layer imports from infrastructure, no folder name will save you.
  • Mentoring. The best leverage in any team is the senior engineer who pairs with the junior every week.
  • Refactors that ship. A great refactor that never reaches production is a worse outcome than an ugly hack that does.
  • Tools over heroics. Codemods, type checks, and good CI beat senior judgment applied at 11pm.

Stack I reach for

Frontend: Vue 3, TypeScript, Pinia, Vite, Tailwind, Vitest, Storybook. Backend: Symfony, PHP, Node, Flask, Postgres, Redis. Tooling: Docker, GitHub Actions, Playwright, Cursor, CodeRabbit. See /uses for the full list.

Outside of work

I build Personal Finance AI, a self-hosted personal finance assistant with a double-entry ledger and a Claude agent. Spanish native, English B2.

Reach me

Email · LinkedIn · GitHub

Career

Timeline.

  1. Senior Software Engineer

    August 2024 — Present

    Sesame HR · Valencia, Spain · Remote

    • Migrated the entire finance vertical from Vue 2 to Vue 3
    • Replaced custom storage with Pinia, cutting state-related bugs by 40%
    • Standardized the provide/inject pattern for context stores
    • Architected an OCR document service with Flask + LangChain + OpenAI
    • Drove adoption of Copilot, Supermaven, Cursor and CodeRabbit across the team

  2. Senior Software Engineer & Tech Lead

    September 2022 — August 2024

    Corporalabs · Madrid, Spain · Remote

    • Built two products from scratch following Clean Architecture and SOLID
    • Led a 5-person team across backend (Symfony) and frontend (Vue 3)
    • Implemented OpenAI embeddings-based product recommender for Pepe Jeans
    • Built a digital showroom for fashion brands

  3. Software Engineer & Team Lead

    February 2019 — September 2022

    Horizm · Alicante, Spain · Remote

    • Joined a 3-person team that grew to 15+ engineers in 2 years
    • Migrated the frontend from PHP templates + jQuery to Vue 2 + internal API
    • Built backend MVC architecture, later migrated to DDD
    • Migrated web scraping from Selenium/PHP to Playwright on AWS Lambda

  4. Software Engineer

    July 2018 — December 2018

    Hello Prêt · Paris, France · Remote

    • Migrated frontend from PHP templates to Vue 2 SPA
    • Maintained Laravel + jQuery legacy code
    • Built WordPress blog and quizzes integrated with Vue app

  5. Frontend Engineer

    September 2016 — July 2018

    DynamicBrain · Alicante, Spain

    • Frontend lead of 5+ developers
    • Worked across Symfony, Sylius, Laravel, WordPress, PrestaShop, Magento
    • Continuous coordination with marketing, art and backend teams