Filip Vavera

Professional Summary

Senior Software Engineer with 12+ years designing, implementing, and maintaining reliable, horizontally scalable distributed systems. Strongest work includes high-throughput, low-latency data pipelines, payments and money-movement platforms, zero-downtime authentication migration, low-level cryptographic protocol implementations, and production LLM/agent integrations. I am hands-on, take initiative, and thrive in flat, meritocratic environments focused on engineering excellence and truth-seeking.

I believe truth-seeking AI is the most important and challenging problem of our time - and understanding the universe is a personal obsession: I maintain open-source Elixir bindings for NASA SPICE and ERFA astronomy libraries among other things.

Actively seeking US relocation; require visa sponsorship.

Core strengths

Reliable, horizontally scalable distributed systems: high throughput, low latency, high availability
Backend and systems engineering in Elixir/Erlang, OTP, Phoenix, SQL, and native C integrations (NIFs)
Data-intensive systems: ClickHouse, PostgreSQL, MySQL, Kafka streaming, workers, and analytics pipelines
Payments and fintech: payment processing, transactions, fraud-sensitive money movement, compliance-aware design
LLM/AI product integration, agent SDKs, and agentic workflow orchestration
Service observability and reliability best practices; security engineering: authentication, SSO, SAML, MFA, OAuth, cryptography

Selected Systems Work

Independent low-level systems work focused on protocol correctness, cryptography, distributed networking, and high-performance native integrations.

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

Work experience

CrazyEgg - Senior Software Engineer

February 2022 - present

https://crazyegg.com/

Lead technical design and implementation of secure, horizontally scalable Elixir backend systems for a high-traffic consumer 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, zero downtime, and high availability.
Built and optimized high-throughput, low-latency data pipelines and background workers processing millions of events per day on ClickHouse and MySQL.
Own service observability and reliability practices (Datadog, Sentry, Grafana) for the systems I ship; built internal tools that improved Customer Success incident response by ~20%.
Prototype and ship AI-assisted features and LLM/agent integrations - agent orchestration, evaluation, and iteration on production workflows for Customer Success and engineering.

BnT - Software Architect

May 2020 - December 2020

https://bntlab.com/

Sole backend engineer on a greenfield gold trading platform: architected and delivered the full backend using Event Sourcing and CQRS under startup-like pace and tight deadlines.
Implemented payment processing, FX conversion, transaction validation, and core domain workflows with rapid prototyping and user-centric iteration.
Collaborated remotely with a small cross-functional team, owning architecture, scalability, and reliability decisions end to end.

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 building a large-scale consumer fintech application 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 - high-concurrency, low-latency money movement.
Built and hardened secure backend services for critical payments, fraud-sensitive credit workflows, and compliance-constrained financial data handling.
Pioneered remote execution as the only distributed engineering team member, relying on strong prioritization and concise, accurate communication 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 Python/Django, React, Node.js, and real-time services.
Built neural-network experiments in PyTorch (2016-17): reinforcement-learning agents for simple control games (pole balancing) and handwritten-digit recognition.
Served as fractional CTO for multiple startups - founding-engineer-style ownership of architecture, implementation, and delivery.

Technical Skills

Languages: Elixir/Erlang, SQL, Python, TypeScript, C (production NIF bindings), C++ (first language, non-professional), Ruby (maintenance)
Frameworks: Phoenix, Phoenix LiveView, OTP
Data & Infra: ClickHouse, PostgreSQL, MySQL, Redis, Kafka (high-volume streaming), Docker, Kubernetes, containerized applications, AWS, Google Cloud
Observability & Reliability: Datadog, Posthog, Sentry, Grafana, Prometheus
Security: Cryptography, Authentication/Authorization, MFA, OAuth, SAML, Protocol Design
Other: LLM integrations, agent SDKs and orchestration, PyTorch (2016-17 RL and vision experiments), Event Sourcing / CQRS, CI/CD, rapid prototyping