Ex-Facebook Engineer Recalls Internal Event Hook System 'Butterfly'

cnakazawa · x · 2026-08-07

Former Facebook engineer Christoph Nakazawa shares insights into the company's highly open internal culture from a decade ago. Employees had access to all codebases and internal comms, could ask Zuck questions directly, and submit Pull Requests to any product.

He specifically highlights Butterfly, an internal event hook system. It allowed employees to listen to internal company events and trigger specific actions, such as running a CI job for specific code path changes or auto-commenting in a team group after a deploy. The author used it to filter company-wide notifications and monitor unauthorized changes to his code.

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