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sgiath.dev

cyberpunk · cryptoanarchy · transhumanism

Filip Vavera

sgiath.dev | [email protected]

Professional Summary

Senior Software Engineer with 12+ years building backend, security, data, and distributed systems. Strongest work includes low-level cryptographic protocol implementations in Elixir, zero-downtime authentication migration, high-scale analytics pipelines, fintech/payment systems, and production LLM integrations. I work best on hard infrastructure problems where correctness, reliability, and fast execution matter.

Actively seeking US relocation; require visa sponsorship.

Core strengths

  • Backend and systems engineering in Elixir/Erlang, Phoenix, OTP, and SQL
  • Distributed systems, event-driven architecture, Event Sourcing, and CQRS
  • Data-intensive systems: ClickHouse, PostgreSQL, MySQL, pipelines, and workers
  • Security engineering: authentication, authorization, SSO, SAML, MFA, OAuth, cryptography
  • LLM/AI product integration and agentic workflows
  • Technical leadership, design review, mentoring, and remote execution

Selected Systems Work

Independent low-level systems work in Elixir, focused on cryptography, protocol correctness, distributed networking, native integrations, and uncommon problem domains.

  • Noise Protocol - Full Elixir implementation of the Noise Protocol framework for secure cryptographic channels.
  • Reticulum - Implementation of the Reticulum cryptographic networking stack for resilient multi-medium networks.
  • Nostr Libraries - Suite of libraries implementing the decentralized Nostr protocol.
  • secp256k1 - High-performance Elixir NIF bindings for Bitcoin’s secp256k1 cryptography library.
  • Domainatrex - Took over maintenance and rewrote the Public Suffix List parser for performance and edge-case correctness.
  • Elixir Astro - Bindings for NASA SPICE and ERFA libraries for advanced astronomical computation.

Work experience

CrazyEgg - Senior Software Engineer

February 2022 - present

https://crazyegg.com/

  • Lead technical design and implementation of secure, scalable Elixir backend systems for a high-traffic analytics product.
  • Rewrote a 20-year-old custom Ruby authentication system to Elixir, including SSO, SAML, MFA, and secure password flows, with full backward compatibility and zero downtime.
  • Built and optimized background workers, SQL queries, and analytics pipelines processing millions of events per day.
  • Built internal operational tools and integrations that improved Customer Success incident response by ~20%.
  • Prototype and ship AI-assisted features and LLM/agent integrations in Elixir for Customer Success and engineering workflows.

BnT - Software Architect

May 2020 - December 2020

https://bntlab.com/

  • Architected and delivered the full backend for a gold trading Proof of Concept using Event Sourcing and CQRS.
  • Implemented payment processing, FX conversion, transaction validation, and core domain workflows as the sole backend engineer.
  • Collaborated remotely with a small cross-functional team under tight deadlines.

DivvyPay (now BILL Spend & Expense) - Team Leader and Senior Software Engineer

April 2018 - February 2022

https://www.bill.com/product/spend-and-expense

  • Led a team of 8 engineers in a fast-growing fintech startup as the company scaled from ~10 to 250+ employees.
  • Owned technical strategy and implementation for payment processing, bank integrations, credit card issuance, and loan systems.
  • Built and improved secure backend services for critical money movement and credit workflows.
  • Pioneered remote execution as the only distributed engineering team member while maintaining reliable delivery across time zones.

profiq - QA Engineer to Fractional CTO

January 2015 - April 2018

https://profiq.com/

  • Progressed from QA automation to full-stack development and technical leadership.
  • Delivered production systems using Django, React, Node.js, and real-time services.
  • Served as fractional CTO for multiple startups, leading architecture, implementation, and delivery.

Technical Skills

  • Languages: Elixir/Erlang, SQL, Python, TypeScript, Ruby (maintenance)
  • Frameworks: Phoenix, Phoenix LiveView, OTP
  • Data & Infra: ClickHouse, PostgreSQL, MySQL, Redis, Kafka, Docker, Kubernetes, AWS, Google Cloud
  • Observability: Datadog, Posthog, Sentry, Grafana, Prometheus
  • Security: Cryptography, Authentication/Authorization, MFA, OAuth, SAML, Protocol Design
  • Other: LLM integrations, Event Sourcing / CQRS, CI/CD