AVAILABLE FOR WEB, FLUTTER & QA PROJECTS
How to use this tool
1. Input Daily Active Users (DAU)
Enter your daily active user count or total target audience.
2. Select Release Risk Profile
Choose High Risk (billing/auth), Medium Risk (core UI flow), or Low Risk (styling/copy).
3. Define Error Tolerance
Set maximum acceptable delta in 5xx errors or client exception rates (e.g. 0.1%).
4. Review Phased Rollout Schedule
Export the phased timeline (Internal -> 1% -> 5% -> 25% -> 50% -> 100%) and automated rollback triggers.
Formula or logic used
Canary Cohort & Statistical Significance Model
Determines minimum user cohort sample sizes and error rate limits needed to detect regressions before full release.
Sample Size: N = (Z^2 * p * (1-p)) / E^2 where Z=1.96 (95% confidence) and E is acceptable error marginCanary Exposure: Users in cohort = Total DAU * (Rollout Percentage / 100)Standard Cadence: 1% Canary (4h soak) -> 5% (8h soak) -> 25% (24h soak) -> 50% (24h soak) -> 100% GARollback Threshold: Immediate automated revert if canary error rate exceeds baseline by 50%
Examples
Example 1: Fintech Checkout Redesign (100,000 DAU)
Limits financial blast radius while collecting statistical proof of payment gateway stability.
Example 2: B2B SaaS Navigation Refresh (10,000 DAU)
Provides sufficient user feedback and telemetry without dragging release cycle past 48 hours.
Common use cases
High-Risk Database Schema Migrations
Deploy dual-write feature flags to 1% of write traffic to verify database latency before cutover.
Mobile App Store Phased Releases
Align backend feature flags with iOS phased releases (1% to 100% over 7 days) to catch crash spikes.
A/B Testing Power Analysis
Calculate whether a small feature flag test cohort will reach statistical significance within the planned sprint window.
Automated CI/CD Rollback Automation
Define quantitative metrics that trigger automated flag kill-switches via Datadog or Sentry webhooks.
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Frequently asked questions
What is the difference between a feature flag and a canary release?
A feature flag toggles code paths at runtime for specific users or percentages, often at the application layer. A canary release traditionally routes server-level network traffic to a new server or container version. Modern practices combine both for granular progressive delivery.
How long should a canary soak phase last?
For high-traffic consumer web applications, 2 to 4 hours is often sufficient to observe error rate anomalies. For lower-volume enterprise B2B apps, 24 to 48 hours is recommended to capture full business cycle interactions.
How do you avoid sample bias when assigning feature flag cohorts?
Use consistent deterministic hashing (such as MurmurHash3 or SHA256 of User ID + Feature Flag Key modulo 100). This guarantees that a user remains in the same cohort across sessions without database state storage.
What should trigger an immediate automated rollback?
Immediate rollback triggers typically include: a 50% spike over baseline in HTTP 5xx errors, unhandled client JavaScript exceptions in the canary cohort, or a measurable drop in checkout conversion.
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