THE ENGINEER BEHIND THE BLOG

Jeffrey Sylvan

Staff / Principal Software Engineer · Distributed Systems, Platform, and AI Infrastructure.
Arlington, MA (Boston area) · remote-friendly.

Email Jeff LinkedIn Resume · PDF GitHub
Selected impact

Staff-level impact, compressed for a ten-second scan.

100s of engineers adopted the delivery pipeline he built First Republic Bank · deploys moved from days to minutes · resume
90% lower server and development cost per game Apocoplay · founder and CTO · team of 20 · resume
1st backend-led production ML application, with full MLOps CarGurus · highlighted on an investor earnings call · resume
10,000 player battle architecture, designed and published in public Black Skies · thesis · benchmark ledger
The short version

I'm Jeff Sylvan, a Staff/Principal software engineer focused on distributed systems, platform engineering, and AI infrastructure.

Before this break I was a Principal Engineer at CarGurus. Earlier work includes production ML infrastructure, delivery systems used by hundreds of engineers, commerce-platform rebuilds at global scale, and real-time multiplayer engines at two game studios, one of them mine.

I stepped away in February 2026 to care for my family. During the break I built Black Skies in public as a work sample: architecture notes, 25 hand-built diagrams, benchmark plans, test evidence, and the implementation record for a 10,000-player real-time battle system, with custom automation and LLM tooling behind the workflow. The goal is simple: show how I reason about Staff-level systems work when there is no interview prompt and no scaffolding. The receipts start at the build ledger.

Impact case notes
CARGURUS · 2023-2026

First ML app out of backend engineering

Led the first non-data-science team to ship a production ML application with a full MLOps pipeline. Highlighted to investors on an earnings call, and the path it opened is now walked by other backend teams.

FIRST REPUBLIC BANK · 2018-2023

Deployments: days to minutes

Built the continuous delivery pipeline that took releases from days to minutes, drove adoption across hundreds of engineers, and trained 50+ engineers, architects, and directors on the practices behind it.

CIMPRESS (VISTAPRINT) · 2015-2017

The rebuild that unblocked the EU

Found the scaling flaw in core commerce infrastructure that compounded with every acquisition and threatened EU sales. Won cross-department buy-in, led the rebuild, and handed a junior team a platform that ran incident-free at thousands of queries per second.

APOCOPLAY · 2012-2015

90% lower cost per game

Founded the studio, led a team of 20, and built a server-side engine for large-scale multiplayer games that cut server and development costs by 90%, saving hundreds of thousands of dollars per title annually.

COGNICLUSTER · 2026

The work sample you are reading

Designed and published the Black Skies architecture solo: eight posts, 25 hand-authored diagrams, 1,000+ test methods and chaos suites passing in the repo, and every unproven claim tagged with the load test that would falsify it.

What the break produced

A career break with receipts. Everything below was designed, written, built, and operated between February 2026 and now, by one person with an orchestrated agent fleet.

THE ARCHITECTURE · 8 POSTS

Black Skies

A 10,000-player battle design with no time dilation, argued in public with diagrams, benchmark plans, and published falsifiers.

Start with the thesis →
THE ORCHESTRATION LAYER · RELATED PROJECT

Ambient Agents

A reconciliation kernel for the agent fleet that builds Black Skies. Designed in public with a published kill condition.

The project →
THE DISCIPLINE

The ledger

What has been measured, what has not, and exactly what would falsify the design. The honesty budget the whole series runs on.

Read the ledger →
THE COMPANY

CogniCluster LLC

The one-person shop behind all of it: sites, infrastructure as code, CI, and the agent fleet, built and operated solo.

cognicluster.com →
Career record
2026 - now
Public work sample during family-care break · Staff/Principal-level systems work, in publicBlack Skies architecture, benchmarks, diagrams, tests, and this blog, built through CogniCluster LLC (a one-person shop).
2023 - 2026
CarGurus · Principal Software EngineerProduction ML out of backend engineering, ADRs and architecture reviews, monolith to services.
2018 - 2023
First Republic Bank · Senior Software Engineer, Principal scopeContinuous delivery adopted by hundreds of engineers; training for 50+.
2017 - 2018
HubSpot · Senior Software EngineerKafka-backed identity and user-data pipelines.
2015 - 2017
Cimpress (Vistaprint) · Lead Software EngineerThe tax-infrastructure rebuild that unblocked EU sales.
2012 - 2015
Apocoplay · Founder and CTO20-person studio; 90% cost reduction per game ported to its engine.
2001 - 2012
Earlier · Allscripts · Council for Logistics Research · PRTM · QScendHospital finance, defense logistics for the Office of the Secretary of Defense, municipal software.

University of Hartford, B.S. Computer Science · MIT certificates in Data Science and Blockchain · MIT Start Smart and Invest Smart.

If you are evaluating me for a role: the resume is two pages, this blog is the work sample, and the fastest honest tour is the thesis followed by the ledger. Email me and I will respond quickly.