# Latency

> Latency is the time between submitting an SMS and its arrival on the handset, typically a few seconds on a healthy route; it is the metric that matters most for one-time codes.

For a code, latency is the product: a user waiting twenty seconds gives up and asks for another. Latency comes from the gateway's processing, the route's hops, the operator's SMSC and the handset's connection. It rises when a route is congested or when messages queue behind a large campaign.

Separate transactional traffic from bulk so that a marketing send never delays a login code, and measure latency per destination rather than as one average.

At SMSMeteor: the status page publishes API and delivery latency percentiles; transactional messages flagged as such are not queued behind campaigns.

Related terms: [Throughput (TPS)](https://smsmeteor.com/glossary/throughput), [OTP (one-time password)](https://smsmeteor.com/glossary/otp), [SMS route](https://smsmeteor.com/glossary/sms-route)

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Source: https://smsmeteor.com/glossary/latency (HTML). Generated by SMSMeteor from the same data as the page. Summary of the whole site: https://smsmeteor.com/llms.txt