Systems Engineer specialized in Performance, Tracing & Reproducible Infrastructure

I am a systems engineer specialized in performance benchmarking of distributed systems and the infrastructure needed to do it reproducibly: fleet provisioning, node operations, deterministic builds, orchestration, and metrics pipelines. I have worked on Linux for more than 20 years, and it has been my only environment for over a decade, from bare-metal point-of-sale terminals to multi-region cloud fleets. My core tools are Nix, Bash, HashiCorp Nomad, AWS, and PostgreSQL, with a decade of Haskell behind them.

I build and operate the benchmarking infrastructure for cardano-node, the software powering the Cardano blockchain. Every cardano-node release is validated on this infrastructure before shipping.

• Performance reports: metrics analyzed down to the millisecond, published with each evaluation. Examples: memory / execution budget evaluation (10.2, 2025) (PDF), release performance evaluation (10.1.1, 2024) (PDF).
• Fleet provisioning and node operations: reproducible benchmarking clusters of 52 AWS machines across three regions, administered directly over SSH and automated with Nix, Bash, and HashiCorp Nomad (extended with a custom plugin). Main PRs: #6544, #6611, #4760, #4852, #5037, #5068, #5129.
• Low-level performance engineering: OS-level tuning such as disk-cache behavior for on-disk benchmarks, and analysis of Haskell runtime memory usage and garbage-collector behavior.

I keep large Nix codebases simple, fast, and dependency-light. On cardano-node, a repository with roughly 520 CI jobs, I restructured the Nix code behind the Hydra CI pipeline for optimized cache hits (#6105): Hydra evaluation time dropped from multiple hours to under 12 minutes, and post-evaluation job processing from over 40 minutes to about 8. This was the final step of a sustained simplification effort (#5957, #5983), not a one-off.

Feedback from the CI infrastructure maintainer after #6105:

"Big improvement from what I've seen already! [...] it looks like there is a solid ~30 minute improvement on the post-eval minimum build time also. Awesome!"

I have been an active member of the Haskell community for more than 10 years, with a merged contribution to Cabal, Haskell's package manager.

• fmaste.github.io/Haskell: Notes on Haskell and theoretical computer science, including type checking and inference, evaluation strategies, and EDSL design (source).
• Helenium: A Haskell EDSL for automated browser testing, in production since 2011, with a web console for creating, editing, and running tests with rich output (screenshots, debug logs, assertions, warnings).
• Mafia: A Cabal alternative with Nix-style reproducible builds, including research notes on GHC internals (2016).

Simplicity first: minimal dependencies and no over-engineering, as the dependency removal and pipeline simplification above show in practice. Testing as a requirement, not an option: unit tests plus property-based testing with QuickCheck and Hedgehog, wired into CI. Code evolves through small, reviewable refactoring steps, with git-bisect as the safety net.

LinkedIn: https://www.linkedin.com/in/fmaste/

B.S. in Computer Science Engineering, ITBA