Feature Flags Cheat Sheet

Patterns for using feature flags to decouple deployment from release, run experiments, and control rollout risk.

2 PagesIntermediateFeb 18, 2026

Types of Feature Flags

Common categorizations of flags by purpose and lifespan.

Release flags- Short-lived, gate an incomplete feature until it's ready; removed after full rollout
Experiment flags (A/B)- Route users into variants to measure impact on a metric
Ops flags- Kill switches to disable a feature or subsystem under load or failure
Permission flags- Long-lived, gate features by plan tier or entitlement

Basic Flag Evaluation

Typical client-side pattern for checking a flag with a fallback default.

javascript

import { useFlag } from 'feature-flag-sdk';function Checkout() {  const newFlowEnabled = useFlag('new-checkout-flow', false); // default: off  if (newFlowEnabled) {    return <NewCheckoutFlow />;  }  return <LegacyCheckoutFlow />;}

Unleash Feature Toggle Config

Example strategy config for a gradual percentage rollout.

json

{  "name": "new-checkout-flow",  "enabled": true,  "strategies": [    {      "name": "gradualRolloutUserId",      "parameters": {        "percentage": "25",        "groupId": "new-checkout-flow"      }    }  ]}

Rollout Strategies

Ways to progressively expose a flagged feature.

Percentage rollout- Gradually increase the share of traffic/users receiving the new behavior
Ring/cohort deployment- Enable for internal users, then beta users, then everyone
Targeted attributes- Enable by user segment, region, or account tier
Kill switch- Instant global disable without a redeploy when something goes wrong

Pro Tip

Treat flags as tech debt with an expiration date — track stale release flags and delete them once a feature is fully rolled out, or the codebase accumulates unreadable nested conditionals.

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