Monitoring OTP Health: SLOs, Error Budgets, and Alerts

Phone verification at scale discussed architecture. This post focuses on operational metrics: what to measure, how to alert, and how to tie OTP reliability to product decisions—without repeating the same paragraphs as our deliverability checklist, which is about message content and templates.

Beyond Generic API Uptime

Your API gateway can return 200 while users still fail login because SMS never arrived or verification timed out. Track end-to-end outcomes: request OTP → user submits code → verify succeeds, segmented by region and client version.

Golden Signals for OTP

Useful starting points: send acceptance rate from your provider, latency from send click to SMS received (sampled with user consent or instrumentation), verify success rate, and cost per successful verification. If you poll status, include delivery state in analytics.

Error Budgets and Product Tradeoffs

If verify success drops below SLO for a week, freeze new auth features and invest in carrier diagnostics or UX copy. Error budgets turn reliability into a shared product decision, not only an on-call problem.

How This Extends Scale Guidance

Indian peak hours and festivals can spike OTP volume— delivery benchmarks help set realistic targets. Pair monitoring with cost visibility so engineering and finance agree when to optimize code versus when to negotiate volume.

FAQ

See FAQ above.