Emit one usage event per completed transcription job, carrying the audio duration as a property, then aggregate by SUM per customer per billing period. That's how to track transcription API usage programmatically in a way that survives an audit. Flexprice handles the aggregation, quota enforcement and invoicing from that single event stream, so your service only has to report what it processed.

Key Takeaways

• The billable unit is audio duration, not API calls, because a 3-second clip and a 90-minute recording cost you wildly different amounts to process.

• Emit the event after the job completes, not on submission, so failed and cancelled jobs never reach an invoice.

• A SUM aggregation over a duration property turns raw events into billable minutes without your service holding any running total.

• Reconciliation is the real work: what your upstream provider billed you and what you billed your customer come from two different clocks and two different rounding rules.

• Flexprice fires threshold alerts on a three-level model (info, warning, critical) for wallet balance or usage, scoped to a customer or a single feature, with a webhook on every state transition.

What should a transcription usage event contain?

Send one event per completed job with enough properties to re-rate later without replaying audio. Flexprice events carry event_name, external_customer_id, properties, timestamp and source.

• Audio duration in seconds, as the property the meter aggregates. Seconds keep rounding decisions in the billing layer rather than in your service.

• The job identifier, so a duplicate delivery can be deduplicated instead of double-billed.

• Model or tier used, since most transcription APIs price a fast model differently from an accurate one.

• Language, diarisation and timestamp flags, if any of them carry a price premium now or might later.

• Completion timestamp, which decides which billing period the minutes land in for long-running jobs.

How do you meter audio minutes for billing?

Define a billable metric that aggregates the duration property, then attach a price to it. Usage Metering supports SUM, COUNT, MAX, LATEST and AVERAGE aggregations, and SUM over duration is what turns an event stream into minutes.

• Bill in whole seconds internally and round once, at invoice time, rather than rounding every job up to a minute.

• Use volume or graduated tiers if longer customers should pay less per minute, and set the model in the contract, since the two produce different totals on identical usage.

• Keep the raw events. Re-rating a disputed invoice needs the original stream, not a monthly total.

• Flexprice's event debugger shows every ingested event, so a customer challenging a number gets an answer from the record rather than a guess.

How do you set quotas and alerts on transcription usage?

Gate on entitlements and warn before the wall. Entitlements cap what a plan tier can consume, and threshold alerts tell the customer before they hit it.

• Flexprice ships four threshold alert types on one info, warning and critical model, monitoring either prepaid wallet balance or usage consumed in the cycle.

• Scope alerts to the whole customer or to a single feature, so a team burning through transcription minutes gets flagged separately from its other usage.

• Every state transition delivers a webhook, which is what lets your product show an in-app banner rather than sending a surprise invoice.

• Handle overage explicitly: charge the payment method on file or block further jobs. Silence is the one option that generates support tickets.