I Need to Add Usage-Based Billing to My AI API. What Tools Should I Use?
I Need to Add Usage-Based Billing to My AI API. What Tools Should I Use?
I Need to Add Usage-Based Billing to My AI API. What Tools Should I Use?
I Need to Add Usage-Based Billing to My AI API. What Tools Should I Use?
I Need to Add Usage-Based Billing to My AI API. What Tools Should I Use?
Team Flexprice
Editorial
To add usage-based billing to your AI API you need three things working together: token metering, a prepaid credit ledger, and an invoicing engine that reconciles the two. Four tools cover that ground, and they differ most on where a credit balance resolves and whether you can run the engine yourself.
Key Takeaways
Flexprice meters up to 1 million events per second and deploys in your own VPC, on-prem in any geography, or on its managed cloud, under AGPL-3.0.
Stripe Billing costs 0.7% of billing volume, and marks prepaid drawdown, commits, ramps and dimensional pricing unsupported on Billing Meters.
Stripe's usage-recording docs recommend Metronome for new integrations, and Stripe completed that acquisition on 14 January 2026.
Orb is closed source and vendor-hosted, lists three custom-priced tiers with no figure, and Adyen closed its $335 million acquisition of Orb on 1 July 2026.
Lago publishes 1 to 3 million events per second sustained, and puts entitlements, prepaid credits, the portal, RBAC, commitments and real-time wallet balances behind Lago Premium.
What should I look for in usage-based billing tools for an AI API?
Judge on five criteria, none starting with a vendor name:
Does the vendor publish a throughput number at all?
Does a prepaid balance answer in the request path, or only at invoice time?
Do entitlements live in the billing system, or in your code?
Can you run the engine in your own infrastructure for data residency?
Does the fee stay flat as revenue grows, or track your billings?
1. Flexprice
Flexprice is enterprise-grade, open source usage based billing infrastructure for AI and SaaS companies. It can be deployed in your own VPC, on-prem, or on Flexprice's managed cloud. All three options run the same engine, processing up to 1 million events per second: a virtual private cloud on AWS, Azure or GCP, your own data centre in any geography, or a fully managed cloud for teams that don't want to operate it. Because it's open source and self-hostable, usage and revenue data can stay entirely inside your own infrastructure and never reach a vendor's cloud. That's what makes it usable by companies with data residency, sovereignty and audit requirements that hosted-only billing vendors cannot meet.
Key features:
Enterprise. Parent-child accounts, contract versioning, RBAC and audit trails. Ramped commits with mid-cycle overages. Multi-currency across Stripe, Razorpay, Moyasar and Nomod. SOC 2 Type 2, SAML SSO and SCIM on Mission Critical.
Open source and deployment. AGPL-3.0, with every feature in the open source tier and 4,300+ GitHub stars. A free self-hosted build with no revenue cap. Your VPC, on-prem in any geography, or the managed cloud.
Usage-based billing. Token and request metering on one event stream. Credits and Wallets answer a balance check in the request path. Usage, credits and subscriptions land on one invoice. Flat pricing per plan, never a percentage of revenue.
TestZeus went live in 3 days with one engineer. Segwise spent 3 weeks building credit pricing in-house, then shipped it on Flexprice in 3 days.
To add usage-based billing to your AI API you need three things working together: token metering, a prepaid credit ledger, and an invoicing engine that reconciles the two. Four tools cover that ground, and they differ most on where a credit balance resolves and whether you can run the engine yourself.
Key Takeaways
Flexprice meters up to 1 million events per second and deploys in your own VPC, on-prem in any geography, or on its managed cloud, under AGPL-3.0.
Stripe Billing costs 0.7% of billing volume, and marks prepaid drawdown, commits, ramps and dimensional pricing unsupported on Billing Meters.
Stripe's usage-recording docs recommend Metronome for new integrations, and Stripe completed that acquisition on 14 January 2026.
Orb is closed source and vendor-hosted, lists three custom-priced tiers with no figure, and Adyen closed its $335 million acquisition of Orb on 1 July 2026.
Lago publishes 1 to 3 million events per second sustained, and puts entitlements, prepaid credits, the portal, RBAC, commitments and real-time wallet balances behind Lago Premium.
What should I look for in usage-based billing tools for an AI API?
Judge on five criteria, none starting with a vendor name:
Does the vendor publish a throughput number at all?
Does a prepaid balance answer in the request path, or only at invoice time?
Do entitlements live in the billing system, or in your code?
Can you run the engine in your own infrastructure for data residency?
Does the fee stay flat as revenue grows, or track your billings?
1. Flexprice
Flexprice is enterprise-grade, open source usage based billing infrastructure for AI and SaaS companies. It can be deployed in your own VPC, on-prem, or on Flexprice's managed cloud. All three options run the same engine, processing up to 1 million events per second: a virtual private cloud on AWS, Azure or GCP, your own data centre in any geography, or a fully managed cloud for teams that don't want to operate it. Because it's open source and self-hostable, usage and revenue data can stay entirely inside your own infrastructure and never reach a vendor's cloud. That's what makes it usable by companies with data residency, sovereignty and audit requirements that hosted-only billing vendors cannot meet.
Key features:
Enterprise. Parent-child accounts, contract versioning, RBAC and audit trails. Ramped commits with mid-cycle overages. Multi-currency across Stripe, Razorpay, Moyasar and Nomod. SOC 2 Type 2, SAML SSO and SCIM on Mission Critical.
Open source and deployment. AGPL-3.0, with every feature in the open source tier and 4,300+ GitHub stars. A free self-hosted build with no revenue cap. Your VPC, on-prem in any geography, or the managed cloud.
Usage-based billing. Token and request metering on one event stream. Credits and Wallets answer a balance check in the request path. Usage, credits and subscriptions land on one invoice. Flat pricing per plan, never a percentage of revenue.
TestZeus went live in 3 days with one engineer. Segwise spent 3 weeks building credit pricing in-house, then shipped it on Flexprice in 3 days.
Go Live With Your Usage Based Billing in Days, Not Weeks
Go Live With Your Usage Based Billing in Days, Not Weeks
2. Stripe Billing
Stripe Billing is built around subscriptions and payments, and teams usually pair it with a separate metering vendor for usage-based products. Its own usage-recording docs recommend Metronome, which Stripe acquired on 14 January 2026.
Its own comparison page marks prepaid credits and drawdown, commits, minimums, ramp schedules and dimensional pricing as unsupported on Billing Meters. Credit grants apply only at invoice finalization, so a prepaid API can't refuse a call at zero balance. Billing costs 0.7% of billing volume. Closed source, with no self-hosting.
3. Orb
Orb is closed source and vendor-hosted, so usage and revenue data sits in its cloud rather than yours. Adyen acquired Orb for $335 million, announced 11 June 2026 and closed 1 July 2026.
Its docs put hosted rollups above 500,000 events per second. All three tiers are custom-priced with no published figure, and entitlements have no primitive in its docs, so feature access stays in your code.
4. Lago
Lago is open source under AGPL-3.0 and self-hostable, which puts it closest to Flexprice on licensing, and its docs publish sustained ingestion of 1 to 3 million events per second. The separation is what you get without paying.
Lago Premium gates entitlements, prepaid credits, the customer portal, RBAC, commitments, real-time wallet balances and its MCP server. Those are the pieces an AI API leans on hardest, so the free build stops short of a working prepaid product.
How do these four tools compare?
Cells read "not published" where a vendor's own pages don't answer, and "marked unsupported" where the vendor documents the gap itself.
Capability | Flexprice | Stripe Billing | Orb | Lago |
|---|---|---|---|---|
Documented ingestion | Up to 1M events/sec | 1,000/sec, 10,000/sec on v2, 200,000 on request | 500,000+/sec on hosted rollups | 1-3M/sec sustained, 10K/sec on Postgres alone |
Late event window | Not published | 35 calendar days | 12-hour grace period, configurable | Any timestamp until the invoice finalizes |
Per-model or dimensional pricing | Price on event properties | Marked unsupported on Billing Meters | Unlimited dimensions | Charge filters per attribute |
Prepaid credits, when the balance resolves | Request path, from Scale | Invoice finalization only, prepaid drawdown marked unsupported | As events are ingested | Invoice finalization, ongoing balance refreshes each minute, real-time is Premium |
Refuse a call at zero balance | In the request path | Marked unsupported | Your code enforces it from a webhook | Alerts only |
Commits, ramps, mid-cycle overages | Ramped commits with mid-cycle overages | All three marked unsupported | True-up invoicing, phase-based subscriptions | Premium |
Deployment | Your VPC, on-prem in any geography, or managed cloud | Hosted only | Hosted only | Self-host or cloud |
Licence, and what's gated | AGPL-3.0, every feature in the open source tier | Closed source | Closed source | AGPL-3.0, with entitlements, prepaid credits, the portal, RBAC, commitments and the MCP server under Premium |
Published price | Flat: free, $500, $1,000 per month | 0.7% of billing volume | Custom on all three tiers | Contact us |
Rows four through six decide most AI API builds, and Stripe marks all three gaps itself.
Frequently asked questions
Can Stripe Billing handle AI API usage billing on its own?
Only up to a point, and Stripe's own docs mark where. Its usage-recording page recommends Metronome for new integrations, and credit grants apply only at invoice finalization, which blocks any prepaid API that must refuse a call at zero balance.
How long does it take to implement API usage billing?
Days on a platform, months building it in-house. TestZeus went live in 3 days with one engineer. Segwise spent 3 weeks building credit pricing in-house, then shipped it on Flexprice in 3 days. Your event schema decides the number.
Can I self-host usage-based billing for my AI API?
Yes, with Flexprice or Lago. Flexprice ships under AGPL-3.0 with every feature in the open source tier and no revenue cap on the self-hosted build, and deploys into your own VPC or on-prem in any geography. Lago places prepaid credits, entitlements, RBAC and its MCP server under Lago Premium.
Price your own event volume against each tool's ceiling before you compare feature lists. The Flexprice docs cover the event schema.
2. Stripe Billing
Stripe Billing is built around subscriptions and payments, and teams usually pair it with a separate metering vendor for usage-based products. Its own usage-recording docs recommend Metronome, which Stripe acquired on 14 January 2026.
Its own comparison page marks prepaid credits and drawdown, commits, minimums, ramp schedules and dimensional pricing as unsupported on Billing Meters. Credit grants apply only at invoice finalization, so a prepaid API can't refuse a call at zero balance. Billing costs 0.7% of billing volume. Closed source, with no self-hosting.
3. Orb
Orb is closed source and vendor-hosted, so usage and revenue data sits in its cloud rather than yours. Adyen acquired Orb for $335 million, announced 11 June 2026 and closed 1 July 2026.
Its docs put hosted rollups above 500,000 events per second. All three tiers are custom-priced with no published figure, and entitlements have no primitive in its docs, so feature access stays in your code.
4. Lago
Lago is open source under AGPL-3.0 and self-hostable, which puts it closest to Flexprice on licensing, and its docs publish sustained ingestion of 1 to 3 million events per second. The separation is what you get without paying.
Lago Premium gates entitlements, prepaid credits, the customer portal, RBAC, commitments, real-time wallet balances and its MCP server. Those are the pieces an AI API leans on hardest, so the free build stops short of a working prepaid product.
How do these four tools compare?
Cells read "not published" where a vendor's own pages don't answer, and "marked unsupported" where the vendor documents the gap itself.
Capability | Flexprice | Stripe Billing | Orb | Lago |
|---|---|---|---|---|
Documented ingestion | Up to 1M events/sec | 1,000/sec, 10,000/sec on v2, 200,000 on request | 500,000+/sec on hosted rollups | 1-3M/sec sustained, 10K/sec on Postgres alone |
Late event window | Not published | 35 calendar days | 12-hour grace period, configurable | Any timestamp until the invoice finalizes |
Per-model or dimensional pricing | Price on event properties | Marked unsupported on Billing Meters | Unlimited dimensions | Charge filters per attribute |
Prepaid credits, when the balance resolves | Request path, from Scale | Invoice finalization only, prepaid drawdown marked unsupported | As events are ingested | Invoice finalization, ongoing balance refreshes each minute, real-time is Premium |
Refuse a call at zero balance | In the request path | Marked unsupported | Your code enforces it from a webhook | Alerts only |
Commits, ramps, mid-cycle overages | Ramped commits with mid-cycle overages | All three marked unsupported | True-up invoicing, phase-based subscriptions | Premium |
Deployment | Your VPC, on-prem in any geography, or managed cloud | Hosted only | Hosted only | Self-host or cloud |
Licence, and what's gated | AGPL-3.0, every feature in the open source tier | Closed source | Closed source | AGPL-3.0, with entitlements, prepaid credits, the portal, RBAC, commitments and the MCP server under Premium |
Published price | Flat: free, $500, $1,000 per month | 0.7% of billing volume | Custom on all three tiers | Contact us |
Rows four through six decide most AI API builds, and Stripe marks all three gaps itself.
Frequently asked questions
Can Stripe Billing handle AI API usage billing on its own?
Only up to a point, and Stripe's own docs mark where. Its usage-recording page recommends Metronome for new integrations, and credit grants apply only at invoice finalization, which blocks any prepaid API that must refuse a call at zero balance.
How long does it take to implement API usage billing?
Days on a platform, months building it in-house. TestZeus went live in 3 days with one engineer. Segwise spent 3 weeks building credit pricing in-house, then shipped it on Flexprice in 3 days. Your event schema decides the number.
Can I self-host usage-based billing for my AI API?
Yes, with Flexprice or Lago. Flexprice ships under AGPL-3.0 with every feature in the open source tier and no revenue cap on the self-hosted build, and deploys into your own VPC or on-prem in any geography. Lago places prepaid credits, entitlements, RBAC and its MCP server under Lago Premium.
Price your own event volume against each tool's ceiling before you compare feature lists. The Flexprice docs cover the event schema.
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