Welcome to my page

My name is Jose Vargas

I am a freelancer from Costa Rica, I offer development and consulting services to grow your software product. I specialize in web app development and eCommerce.

You should work with me because:

  • I will make sure your product feels valuable to your users.
  • The product we build will last for years, I will make sure you don't forget any important detail.
  • I have professional experience working on every layer of large web applications: I can build your UI, improve your UX, build the server-side infrastructure, add third-party integrations, design a database, improve performance, configure a CI/CD pipeline, and add the relevant documentation so that other engineers can get up to speed with ease.

I specialize in the following technologies:

  • TypeScript, Elixir, Rust, Clojure, NixOS, Docker, PosgreSQL, AWS.
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.

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-docs

    Grammar reference with 41 railroad syntax diagrams and cross-linked navigation.

  • 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)

  • phoenix_live_view

    Docs: Update sample code for on_mount authentication.

  • ecto

    Docs: Clarify Ecto.Query filtering behavior.

  • livebook

    Docs: Clarify running Livebook inside a Mix project.

TailwindCSS— Utility-first CSS framework
Neovim— Modal text editor plugins
  • telekasten.nvim

    Create subdirs when creating new note

  • nvim-cmp

    Docs: Expand docs for select_next_item select_prev_item

Emacs— Extensible text editor ecosystem

Hobby Projects

  • My blog[link]

    Built with Rust. How I did it & GitHub.

  • Movie search front-end[link]

    A small project to showcase ReactJS with Typescript, TailwindCSS and Jest. GitHub.

  • Yin Yang Fractal Animation[link]

    A geometric animation created with C++ and the OpenFrameworks library. Try to imagine what it looks like before you open the link! GitHub.

  • This portfolio[link]

    Built with NextJS and TailwindCSS. GitHub.

Professional Services

I can help you with the software development of your project. Whether you are starting your project from zero or you need help extending an existing project I can help you succeed, from product ideation to software implementation. Reach out in one of the platforms below.

Pricing

I am currently available to work with new clients. The pricing depends on the characteristics of the job, you can calculate the hourly charge by selecting the qualities of the job. Alternatively, I prefer working for a day-rate, in which case the price will be lower than the hourly rate shown here. Full-time offers are also considered.

Quality
Included
Hourly cost
Baseline
80 USD
Open Source Discount
-20 USD
Fixed Schedule
10 USD
Daily meetings
10 USD
Managerial role
20 USD
Total hourly cost:
80 USD

I can offer dynamic pricing, for example, if you want some fixed hours of work when we may collaborate, but other hours are flexible. Get in touch with me and we will iron out the details.

Online Presence

GitHubLinkedInStack Overflow
josepablov+biz@gmail.com

Please, no soliciting for unpaid work. Equity does not count as payment.