Simon Willison’s Weblog


5 items tagged “featureflags”


At The Guardian we had a pretty direct way to fix this [the problem of zombie feature flags]: experiments were associated with expiry dates, and if your team’s experiments expired the build system simply wouldn’t process your jobs without outside intervention. Seems harsh, but I’ve found with many orgs the only way to fix negative externalities in a shared codebase is a tool that says “you broke your promises, now we break your builds”.

jbreckmckye # 10th July 2023, 6:53 pm


Product Hunt Engineering Principles (via) Product Hunt implement “Collaborative Single Player Mode”, which they define as “A developer should be able to execute a feature from start to finish -- from the database to the backend, API, frontend, and CSS. The goal is never to get blocked.” I’ve encountered this principle applied to teams before (which I really like) but not for individual developers, which I imagine is more likely to work well for smaller organizations. Intriguing approach.

They also practice trunk driven development with feature flags: “Always start a feature with a feature flag and try to get something to production on day 1.”

And “If a product decision is missing, try to make this decision yourself—it’s better to ask for forgiveness rather than permission.” # 16th August 2021, 3:35 pm


How we use “ship small” to rapidly build new features at GitHub (via) Useful insight into how GitHub develop new features. They make aggressive use of feature flags, shipping a rough skeleton of a new feature to production as early as possible and actively soliciting feedback from other employees as they iterate on the feature. They static JSON mocks of APIs to unblock their frontend engineers and iterate on the necessary data structures while the real backend is bring implemented. # 2nd January 2020, 4:30 am


Feature Toggles (aka Feature Flags). I’m a huge fan of feature flags as a way of managing feature releases and keeping incomplete code in master as opposed to maintaining long-running branches. Recently I’ve found myself pointing people to this essay by Pete Hodgson—it’s a great overview of feature flags (here called toggles) and I particularly like how it splits them into four categories: Release Toggles, Experiment Toggles, Ops Toggles and Permissioning Toggles. # 25th June 2019, 9:13 pm


How we deploy new features. GitHub are experimenting with using Redis for configuration management. I’ve been thinking about this recently too—managing feature flags feels like an ideal use-case for Redis, since it lets you read multiple values on every page access without adding a bunch of extra read traffic on your regular database. # 8th July 2010, 10:04 am