I'm Alex Carter
I build developer tooling, real-time collaboration platforms, and AI-powered products. Currently shipping the agent runtime at Lumen Labs. Previously at Atlassian and Stripe.
Realtime systems
Collaboration engines, CRDTs, sync protocols, and the operational reality of running them at scale.
AI agent runtimes
DAG-scheduled, sandboxed, replayable execution layers for in-product LLM features.
Developer experience
Tools, docs, and APIs that make the right thing the easy thing — and the wrong thing loud.
Lumen Copilot agent runtime
Designed and shipped the agent runtime powering Lumen Copilot — DAG scheduling, sandboxing, deterministic replay. p95 latency 4.2s → 1.8s, failure rate 18% → 2.4%.
realtime-crdt
Open-source TypeScript CRDT library for collaborative editors. Used in production at Lumen Labs and two YC startups.
llm-eval-runner
Reproducible LLM evaluation harness with caching, fixtures, and CI integration. The eval tool I wish I had three years ago.
Jira automation rules engine
Owned at Atlassian. Shipped trigger throttling that fixed runaway loops impacting ~3% of customers.
Speaker at JSConf US — "Realtime UIs without WebSockets"
2025Promoted to Senior at Lumen Labs; led the collaboration-engine rewrite
2024AWS Solutions Architect Associate + CKAD certified
2023Open-sourced realtime-crdt; crossed 1k GitHub stars
2022BSc Computer Science, UC Berkeley — graduated with honors
2018