I'm building a server-side experimentation setup for a web app

Great — a server-side experimentation setup is a solid choice for performance, control, and cleaner client code.

A typical setup looks like this:

1. Experiment assignment happens on the server

   • When a request comes in, the server determines which variant the user gets.
   • Assignment should be deterministic when possible so the same user gets the same variant across requests.

2. Persist the assignment

   • Store the assigned variant in a cookie, session, user profile, or signed token.
   • This prevents users from bouncing between variants.

3. Expose the variant to the frontend

   • Render it into the HTML, send it through an API response, or include it in page metadata.
   • The client can then adjust UI or behavior if needed.

4. Track exposure and conversion

   • Log when a user is actually exposed to a variant.
   • Separately log conversion events so you can calculate impact accurately.

5. Use a feature flag or experimentation service

   • You can build this yourself or use a platform like LaunchDarkly, Optimizely, GrowthBook, Statsig, or Unleash.
   • These help with targeting, rollout rules, bucketing, and guardrails.

6. Be careful with caching

   • If your app uses CDN or server caching, make sure variant-specific content doesn’t get mixed across users.
   • Often this means varying by cookie or disabling cache for experiment-specific pages.

7. Plan for analysis

   • Decide upfront on metrics, sample size, and how you’ll handle segmenting, ramp-up, and stopping rules.

If you want, I can help you design:

• a simple custom architecture
• a database schema for assignments and events
• a middleware-based implementation
• or an end-to-end example in your stack (Node, Python, Ruby, Go, etc.)