Paul Shynin

Case Studies

Production systems I worked on at Peloton from 2019 to 2026, and the independent work I’ve done since March 2026. Each row names the problem or the decision; the case studies show what changed.

Production experience

Peloton, Sep 2019 – Feb 2026: commerce, checkout and reliability.

  • Platform architecture

    Cart-Checkout Platform

    Rebuild the checkout monolith, or buy the commerce backbone and build one checkout layer in front of it: the second let funnels move across one at a time.

  • Migration & rollout

    Warranty Checkout Migration

    Which funnel goes first: small enough to recover from, complete enough to exercise every part of the checkout path.

  • Build vs. buy

    Catalog Migration to Commercetools

    A multi-million-dollar contractor proposal, or a pipeline the team could already debug on call: build or buy for permanent infrastructure.

  • Reliability

    Checkout Observability & Reliability

    Incidents were an ownership problem before they were a tooling problem, so the ownership map came before the monitors.

  • Platform simplification

    Legacy Catalog Service Retirement

    A redundant service nobody could justify a quarter to remove: argued as risk instead of cleanup, then retired consumer by consumer.

  • Testing & CI/CD

    CI/CD and Testing Modernization

    A flaky end-to-end suite had trained the team to ignore red runs; auto-waiting removed the cause instead of the symptom.

Independent work

Since Mar 2026: developer tooling for AI coding agents, applied AI, evaluation and data.

  • Developer tooling

    AgentGrid: coordination for parallel coding agents

    Two agents editing the same file is a coordination problem, not a prompting one, so the rules live in a deterministic policy layer with no model logic.

  • Agent workflow method

    agent-playbook

    How the work is split when agents write code: an Architect session plans vertical slices, each slice gets its own worktree and worker session, a fresh Reviewer checks every PR, and no agent merges.

  • Applied AI, early and private

    Cortex

    Getting model output that code can use: three passes on local models, JSON into typed records, and explicit fallbacks when a response doesn't parse.

  • Contract work

    AI coding-model evaluation

    Judging generated patches the way a reviewer would: apply them to the repository, run the tests, and score correctness and engineering quality.

  • Own project

    Scheduled data pipeline

    Python on OCI with PostgreSQL: runs on a schedule, scores what it collects, alerts on it, and feeds a dashboard.