Gradual Frontend Rollout Without Feature Flags: Just a Cookie and Random Number

arpit_bhayani · x · 2026-08-18

Presents a minimalist approach to gradual frontend rollouts without a dedicated Feature Flag service:

Core Mechanism

On first visit, generate a random integer (1-100) and store it in a cookie.
Define a rollout threshold on the server (e.g., 30). If the user's cookie value ≤ 30, serve the new version; otherwise, serve the old one.

Benefits

Smooth Scaling: Increase the server-side threshold (e.g., 30 to 60) to expose the new version to more users without changing the experience for existing users.
Instant Rollback: Decrease the threshold to revert users above the cutoff back to the old version.
Zero Dependencies: No need for external flag services or session stores—just a cookie, a random number, and a single comparison.

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