The One‑Page Rollback‑Safety Spec for Early Monetization

Keep the spec to a single page with clearly labeled sections: Purpose, Rollout Plan, Acceptance Tests, Billing Controls, Telemetry Smoke Tests, Rollback Criteria, and Postmortem Checklist. The goal is a readable artifact that a contractor can use during a deploy or an incident without reaching into multiple docs.

Include concrete fields (not prose): flag name and ID, server/client evaluation points, feature owner, initial target cohort, percent rollout schedule, exact acceptance test commands and expected outputs, billing write types created (invoices, subscriptions, metered events), and a kill switch action with command snippets or dashboard links.

Treat feature flags as runtime controls, not code hacks. Design them so flipping the flag immediately prevents further billing writes and exposure. Evaluate flags both server‑side (to stop billing writes) and client‑side (to avoid showing charge UI). Put the authoritative billing decision on the server evaluator.

Add metadata to every flag: intent (experiment vs permanent), removal date, expected lifetime, owner, and a documented rollback runbook. Prefer percentage rollouts (canary → ramp) and require a kill‑switch link or API snippet in the spec so anyone can revert the change quickly.

Write acceptance tests as runnable commands that a contractor can execute with one copy/paste (cURL or script). Tests must include: synthetic user signups, hitting the chargeable endpoint, and inspecting the billing write result (invoice created, subscription updated, metered event recorded). Each test line must state expected status codes and the exact fields to inspect in the billing response.

Billing rollback controls are separate from flags. Predefine idempotent remediation paths: a script to void an invoice, an API call to remove a metered event and reprocess usage, and a customer audit query that lists affected accounts. Store these scripts where on-call can run them, and include a templated customer message for refunds or corrections.

Define three telemetry smoke tests that run automatically on rollout and on every deploy: error‑rate spike, payment failure rate, and activation funnel conversion. Telemetry must be tied to the flag—capture flag exposure in the event schema so you can slice metrics by exposed vs unexposed cohorts instantly.

Set clear, objective gate thresholds (for example: error rate > 3× baseline, payment failure rate increase > 2×, or activation drop > 20% in the first 24 hours). If any gate trips, the spec must require immediate flip of the flag and initiate the billing rollback runbook if billing writes occurred.

Before flipping to any live customers, run the preflight: run acceptance tests, verify flag evaluation on server and client, confirm billing write idempotency in a sandbox, and verify telemetry ingest for flag_exposure. Record the timestamp, operator name, and exact percent you’re enabling in the spec.

After a rollback or a full rollout, document the postmortem fields directly on the one‑pager: what tripped the gate, list of affected accounts, remediation steps taken (including refunds), and a clear exit criteria for reattempting rollout. Schedule a flag cleanup task with an owner and date to remove the toggle once stable.