SMS API benchmarks

All metrics reflect a trailing 90-day window. Point-in-time load tests don't capture the variability of a production system handling thousands to millions of requests daily, so we use a longer window to surface the effects of system congestion and public incidents without penalizing providers that are actively improving.

Volume represents the total number of sampled SMS API requests routed through Knock during the period. Because Knock is an orchestration layer, we cannot influence the sending patterns of our customers, so volume varies by provider. To normalize for this, we group providers into volume bands that indicate how statistically confident we are in the observed metrics. Providers with low volume are flagged so you can weigh the results accordingly.

Response time is measured as the elapsed time from when Knock sends an API request to when the provider returns a 200 status indicating message acceptance. We compute percentiles (p50, p90, p95, p99) using exact quantile functions. The measurement includes HTTP connection pooling time and network latency, applied consistently across all providers. This measures API acceptance latency, not end-to-end delivery to the recipient's phone.

Error rate is the ratio of requests that received a 5xx status code to total requests for the period. Knock automatically retries failed requests, so a single request can produce multiple error entries if each retry also fails. We believe this accurately represents the provider's availability during those periods.

In Knock, a connection to a provider API is modeled as a channel. Growth rank reflects how many new channels were created for each provider during the 90-day window. To detect directional trends, we split the window into two 45-day halves and compare them, producing the trend indicators (up, down, or stable) shown alongside each rank.