William Ferreira

Remote · Finance Analytics · grafiniti.com

• Built long-running, queue-driven AI agents for finance workflows — stateful systems that run RAG-backed, multi-step reasoning over fund data and persist state across extended runs. The frontend enqueues analysis requests; the agent polls the queue and processes them asynchronously.
• Built natural-language query tooling over platform data, and a Model Context Protocol (MCP) server exposing that data to internal AI agents with OAuth and cross-service routing.
• Designed a unified resource-sharing and permission layer across multiple product surfaces — access at user, team, and org levels, with expiration policies and audit logs.
• Built a major reporting and data-composition feature end to end, from data models and APIs through to a multi-step report builder and public sharing.
• Optimised heavy analytics queries with targeted indexes, planner statistics, and a batched recalculation flow resilient to dead processes.
• Built a separate Next.js product end to end as sole author (SSO from the main app, S3-hosted assets, RBAC), plus the internal admin portal covering organisation onboarding, multi-tenant access management, and operational dashboards.
• Designed the multi-tenancy and permission model alongside the CTO, including a substantial refactor of the org-membership layer.

StackPython, Flask, SQLAlchemy, pytest, boto3, AWS, GCP, DuckDB, Auth0, Coolify, MCP, Anthropic, Gemini, LangGraph, Next.js, React, TypeScript, Tailwind, OpenAPI 3.0

Remote · Podcasting Platform · sacocheio.tv

• Rebuilt the main site and admin dashboard from React/Express to SvelteKit, modernising frontend performance and cutting memory usage by ~70%.
• Automated migration of media hosting to a video CDN via custom Python scripts, eliminating buffering issues behind ~70% of support tickets.
• Deployed Owncast on DigitalOcean for HLS live streams, cutting streaming costs by 66% while gaining full operational control.
• Integrated Stripe subscription flows and designed a pay-per-view system, almost doubling paid conversions and opening new monetisation channels.
• Refactored an Express.js microservice (RSS feeds + payment webhooks) into Java 21 with Javalin; added live chat and real-time viewer counts using Quarkus.
• Migrated the primary database to PlanetScale with primary/read replicas, cutting query latency by 90%.

StackSvelteKit, Svelte 5, React, Next.js, Java 21, Javalin, Quarkus, Go, Python, Prisma, Tailwind, tRPC, MySQL, PlanetScale, Cloudflare, BunnyCDN, MUX, Owncast, ffmpeg, nginx, Caddy

Remote · Staffing / Contract · lithiumsoft.com

• Virtual Therapy App: built a full-text search feature with Hibernate Search 6 (Lucene) in a Spring Boot/Axon event-driven backend; implemented multi-tenant security with Spring Security + Auth0; built admin reporting for usage metrics; enhanced anonymous group chat with WebSockets.
• Lighting Network Management (OpenWRT fork): extended the LuCI (Lua) backend for a custom web interface; scripted Bash/Lua daemons and cronjobs on embedded devices; designed a novel Layer 2 communication protocol using Scapy for streamlined device discovery and network adoption.

StackJava 17, Spring Boot, Axon, Hibernate Search 6, Auth0, Azure, React, TypeScript, Lua, Bash, Python (Scapy), OpenWRT, LuCI, SQLite3, Docker

Remote · LawTech / FinTech · prev.app

• Worked alongside the CEO to scope, design, and deliver new features in Java microservices on AWS, accelerating roadmap velocity.
• Engineered a generic benefit-calculation feature, enabling a product launch 18 months ahead of schedule and beating competitors to market.
• Integrated PIX (Brazil’s real-time payments system) into the proprietary payment gateway, streamlining transactions and improving user trust.
• Developed a regex-based PDF scraper to auto-extract benefit data, reducing manual entry by 90% and populating a centralised data lake.

StackJava 11, Spark Java, Google Guice, Docker, AWS (ECS, S3, RDS, Lambda), MySQL, Redis

Florianópolis, Brazil · FinTech · sinqia.com.br

• Implemented core logic for a generic electronic voting system and loan-eligibility calculations, with DocuSign integration for electronic contract signing.
• Collaborated with actuaries to codify complex fee structures into the application, bridging finance and development teams; mentored two junior developers.
• Automated critical day-to-day processes, reducing manual task time for the key client account.

StackJava 8, Spring Boot, Angular 9, JSP, MySQL

github.com/wKoja/thrustmaster-led-linux · write-up

• Built a native Linux daemon that drives the RPM shift LEDs on Thrustmaster racing wheels from live sim telemetry, with multi-hardware auto-detection across 8 wheel-base models — a Linux-native replacement for proprietary, Windows-only tooling.
• Built a real-time 60 Hz telemetry pipeline and integrated systemd/udev services for automatic device lifecycle management.
• The underlying LED control protocol was reverse-engineered in prior work by prodigal.knight; my contribution is the Linux integration, packaging, and device handling.

StackPython 3.11+, HID (hidraw), udev, systemd, Linux, Bash