Software Engineer & Consultant

Jose Vargas

I build systems from zero, contribute to open source, and grow teams. Based in Costa Rica, I offer development and consulting services to grow your software product.

Open Source Contributions
OpenCode—AI coding agent ecosystem
  • opencode

    UX improvement: sort session picker by full updated timestamp while keeping order stable while browsing.

PowerSync—Offline-first sync engine for SQLite, PostgreSQL, MongoDB and MySQL
  • powersync-service

    Detect silent Postgres WAL slot failure mid-sync and abort early instead of completing a doomed hours-long snapshot, with budget monitoring and actionable error guidance. (20+ review comments)

  • powersync-service

    Railroad diagram generation from EBNF grammars for sync-rules documentation.

  • powersync-service

    Redesign Postgres compaction algorithm — replace a fragile unicode sentinel approach for prefix-matching data groups with exact key lookups, eliminating sequential table scans in favor of efficient index access across 12 packages.

GraphQL—API query language and tooling
Elixir—Fault-tolerant real-time web apps
  • livebook

    Add doctest decorations to Monaco editor per result.

  • ecto

    Support preloading associations in embedded schemas from the parent schema.

  • phoenix_live_view

    Docs: Explain sockets as a server-only data struct (merge commit)

Pricing

I contribute to the frameworks your stack runs on. The sections above show what I ship to production OSS; I bring the same standard to client work. Flat rate of 70 USD/hour, lower at a day-rate or for full-time engagements.

Blog posts

  • Making a web app that sends and receives emails[link]

    Golang
    AWS ECS + Fargate
    Pulumi

    I built an simple email client and deployed it to AWS ECS with Pulumi. This was done as an attempt at applying to a company.

  • Verify HMAC signatures in Deno[link]

    TypeScript

    Here I explain how to verify cryptographic HMAC signatures with TypeScript in Deno, and by extension in the browser as well. In this specific example I demonstrate how to verify these signatures for Paddle Webhooks.

  • NixOS Minecraft Server in AWS[link]

    NixOS
    Rust

    This is a tutorial on how to deploy a NixOS server to AWS EC2 from a MacOS computer. In the exercise the server instance is utilized to host a videogame (Minecraft) that other players can join. Uses Docker for building and deploying the NixOS from the local computer to AWS EC2. Includes a custom SystemD service that I wrote in Rust to monitor the server and turn it off automatically when there are no players connected to the game.

  • Making my Static Blog Generator[link]

    Rust

    Covers how I created my own Static Site Generator using the Rust programming language. This is the project that I currently use to publish my blog. The article is aimed at people who are in the process of learning Rust and desire to also create their own blog.

Online Presence

Personal
GitHub|LinkedIn|Stack Overflow
Business
Mural Systems — we build and staff your product
Inquire
josepablov+biz@gmail.com