I built 2,000 badges for Replay and I’m not sure I’ve slept since December

Temporal's Senior Developer Advocate built 2,000 interactive electronic conference badges for the company's annual Replay conference. The badges run on ESP32-S3 microcontrollers with OLED screens, IR transceivers, joysticks, haptic feedback, LED matrices, and gyroscopes. Firmware is written in C with a MicroPython layer so attendees can write their own apps. The author used Claude, Claude Code, and Codex extensively to write firmware despite having no prior embedded C experience, generating ~5,000 lines of production code backed by 21,000+ lines of architecture documentation. Manufacturing involved coordinating with Elecrow in Shenzhen over WhatsApp, a clean-device China trip under strict corporate security policy, and creative workarounds for battery and screen sourcing. The badges are open source and hackable post-conference, with one attendee building a tamagotchi during the event. Future plans include switching to Raspberry Pi RP2350 and running Temporal's Rust SDK on each badge as a distributed worker.