One more update. I spent a little time the other day trying to find all the feature flag products I could. I'm sure I missed a ton. Let me know in the comments!

LaunchDarkly Split Apptimize CloudBees ConfigCat DevCycle FeatBit FeatureHub Flagsmith Flipper Flipt GrowthBook Harness Molasses OpenFeature Posthog Rollout Unleash

Here's my first draft of the questions you'd want to ask about any given solution:

    Questionnaire
    
    - Does it seem to be primarily proprietary, primarily open-source, or “open core” (parts open source, enterprise features proprietary)?
      - If it’s open core or open source with a service offering, can you run it completely on your own for free?
    - Does it look “serious/mature”?
      - Lots of language SDKs
      - High-profile, high-scale users
      - Can you do rules with arbitrary attributes or is it just on/off or on/off with overrides?
    - Can it do complex rules?
    - How many language SDKs (one, a few, lots)
    - Do feature flags appear to be the primary purpose of this company/project?
      - If not, does it look like feature flags are a first-class offering, or an afterthought / checkbox-filler? (eg. split.io started out in experimentation, and then later introduced free feature flag functionality. I think it’s a first-class feature now.)
    - Does it allow approval workflows?
    - What is the basic architecture?
      - Are flags evaluated in-memory, locally? (Hopefully!)
      - Is there a relay/proxy you can run in your own environment?
      - How are changes propagated?
        - Polling?
        - Streaming?
      - Does each app retrieve/stream all the flags in a project, or just the ones they use?
      - What happens if their website goes down?
    - Do they do experiments too?
      - As a first-class offering?
    - Are there ACLs and groups/roles?
      - Can they be synced from your own source of truth?
    - Do they have a solution for mobile and web apps?
      - If so, what is the pricing model?
      - Do they have a mobile relay type product you can run yourself?
    - What is the pricing model?
      - Per developer?
      - Per end-user? MAU?