In January 2024, AssemblyAI, a leading AI speech technology company, faced a challenging three-month deadline to migrate to a new billing platform after their vendor unexpectedly shut down. Leading this critical transition was Mary Pat Colandro, Senior Engineering Manager, whose extensive experience spans building a homegrown system, transitioning to usage-based billing vendors, managing a hyper-growth product platform, and ensuring smooth customer billing experiences. Drawing on this expertise, Mary Pat guided her team to select Metronome as their next billing partner and successfully completed the migration within the tight timeline. 

Below, Mary Pat shares her lessons learned, practical insights, and key considerations for selecting the right usage-based billing vendor for a scalable, efficient, and customer-focused billing solution.

When to start thinking about partnering with your first billing vendor

In its early days, AssemblyAI relied on a simple, homegrown billing system that ran periodic jobs every 10 minutes to report unsegmented usage data. This system lacked the ability to break down costs by product, and customers paid a flat fee for access to all models and downstream services. While functional for a small user base, the system wasn’t scalable. It created risks such as inaccurate billing and difficulties for customers who wanted to pay only for the services they actually used.

Recognizing these limitations, AssemblyAI began evaluating billing vendors capable of supporting product-specific pricing. At the time, there were few vendors on the market that significantly improved on AssemblyAI’s internally built system. Nonetheless, AssemblyAI saw the value of partnering with a dedicated billing provider. This transition introduced much-needed flexibility, allowing customers to pay based on actual usage and optimize their costs. Outsourcing this complexity also freed up their internal teams to focus on innovation and other strategic priorities, ensuring the business could scale without being constrained by its billing infrastructure.

Key takeaway: Proactively addressing when your systems may outgrow business needs can save significant headaches later. Plan for growth early to maintain efficiency and deliver a seamless customer experience.

Nonnegotiables for usage-based billing vendor selection

Today, having been through multiple rounds of billing vendor assessment and supporting the growth of the company's products and customer base, Mary Pat’s list of nonnegotiable requirements is short, but critical.

Nonnegotiable #1: Invoice processing speed and alert latency

AssemblyAI serves a range of customers, from free users to prepaid pay-as-you-go (PAYGO) and enterprise customers. While enterprise customers drive the majority of product usage and revenue, the self-serve segment dominates in sheer numbers. Their product-led growth (PLG) motion has been key to getting developers to first try, then adopt their products, without an upfront commitment.

While handing off their billing management to AssemblyAI’s first billing partner was an improvement, it wasn’t smooth sailing from the start. Soon after onboarding with their new billing vendor, there was a situation.

“We had a fire drill. Free customers were overusing the product, alerts weren’t firing in time, and we had no way to enforce our billing limits quickly enough ”

A 10-minute lag between customers exceeding their credit limit and triggering that alert could cost AssemblyAI up to $50,000 from a single fraudulent user. The same risk extends to their PAYGO customers, another crucial segment of their customer base. This high-stakes lesson underscored the critical importance of choosing a vendor capable of handling massive event volumes while calculating spend in real-time across their growing customer base—making it a top priority for any future vendor evaluations.

Questions to Ask:

• What is the SLA for invoice processing speed and alert latency?
• Can the platform handle spikes in usage or event volumes?

Nonnegotiable #2: scalability

Similar issues quickly followed due to the high volume AssemblyAI ran through their vendor’s API, to the point that it nearly brought down the system. “They told us to stop running our stuff—that they couldn’t support it.” At the time, as an early-stage startup with plans to grow a lot—and quickly—this wasn’t quite what they needed to hear. Now, Mary Pat and her team hone in on the vendor’s future plans to make sure they’re aligned on the magnitude and speed of scale.

“Understanding what level of scale they can support and what is on their roadmap is super important,”

Mary Pat says. “Understanding what’s on their roadmap gives you a clear indication of where they're heading, where they're investing, and making sure that aligns with your goals for the foreseeable future.”

Questions to Ask:

• What scale can your platform handle today?
• What’s on your roadmap to support growing customers?
• Have you experienced performance issues in the past 12–24 months?

Nonnegotiable #3: customer billing experience

One newer requirement Mary Pat and her team would use to vet a new billing partner is the vendor’s ability to help them meet customers’ continuously evolving expectations for the billing experience. Transparency is a critical component of a great customer experience when dealing with usage-based pricing models. This time around, AssemblyAI knew they needed to be able to clearly show customers where they’re spending their money and how their usage is tracking—whether prepaid or PAYGO. Along with that comes the ability for customers to set spend thresholds and alerts, as well as easily access their invoices. AssemblyAI now has all of this in place with Metronome, enabling them to continually elevate their customer billing experience.

Questions to Ask:

• Does your platform offer dashboards, alerts, and spend controls for customers?
• How customizable are spend breakdowns and alerts?

Nonnegotiable #4: vendor’s financial stability

Another critical aspect AssemblyAI has learned to consider from the start that might not come to mind at first is the financial stability of the vendors under consideration. When Mary Pat and her team were searching for their first billing platform vendor, there weren’t a lot of options, so they made the best choice they could at the time. There was no way for them to know that their billing partner would get acquired within the next two years, forcing them to go back on the market for a new vendor, and quickly.

Questions to Ask:

• Who are your key customers, and how long have they been with you?
• What is your company’s funding status and long-term viability?

Choosing Metronome

Faced with a tight 3-month deadline to find a new billing partner, Mary Pat drew on her experience from AssemblyAI’s first billing transition to define key criteria for their next vendor. Metronome ticked all the boxes for what AssemblyAI needed at the moment and to scale flexibly with them as they grew.

Addressing each customer segment’s unique billing needs

In serving a range of customers from free to enterprise, Mary Pat knew that each group has unique billing needs. AssemblyAI introduced free credits, which users access simply by signing up, in the summer of 2024 with Metronome’s support. As customers begin using AssemblyAI’s models, they’re able to track their credit drawdown. In contrast, self-serve PAYGO customers pay upfront and need to know how much they’ve used and how much is left. They also need to be able to see spikes in usage, or anything else that might change their spending plans. Enterprise customers need to know how they’re tracking in relation to their commitment—some may also require the ability to view their current spend broken down by department or project.

“The features to support the customer billing experience are a must-have. We want to be as transparent as possible. So we needed to partner with a mature company that can support those use cases,”

says Mary Pat. Each customer segment has unique needs, and having a single billing platform that can handle them all is key.

Strong partnership makes billing migration easier

Changing billing vendors isn’t for the faint of heart. It requires that you define usage events, structure them appropriately, map everything properly, and more. Getting these things wrong can put you in a bad place in the future, so the pressure that comes with getting it right can be stressful. Mary Pat and her team appreciated having a proactive partner in the process to make sure they were on pace to migrate before their other billing service was deprecated.

“From the get-go, Metronome provided us with a weekly plan that acknowledged our limited bandwidth and short launch timeline. The team was there to partner with us and was very hands-on to help figure out how we would migrate successfully.”

In roughly eight weeks, AssemblyAI’s migration to Metronome was complete, thanks to tight collaboration and lots of hands-on support, says Mary Pat. “We had almost daily syncs with the Metronome team, which isn’t something you can expect from a lot of companies. Any time we asked questions, we got responses very quickly. That was critical, and the Metronome team really spent the time to make sure that we were successful.”

After day 1: meeting pricing management challenges with ease

Across the AI industry, companies are racing to iterate and lower their costs, passing that benefit on to customers. As AssemblyAI has continued to optimize their speech-to-text models, they’ve reduced prices roughly twice in the past 12 months, requiring sweeping changes to their pricing. Enterprise customer contracts also often have lower negotiated pricing, and whenever new features launch, the same functionality comes into play—they must be able to amend pricing to add that specific feature to the pricing model.

Before working with Metronome, launching new products required a slew of manual work, adding the new product to every pricing plan and every contract, or pricing structure. If they introduced a new feature, that meant that every single customer’s prices had to be updated individually.

With Metronome, things are different.

“It's easy for finance and sales to self-serve, without engineering involvement. In the past, our engineering teams had to be very much involved in every single change,”

Mary Pat says. “The Metronome 2.0 model makes it so engineering doesn’t have to be involved at all.” AssemblyAI’s recent pricing reductions went smoothly and quickly, and the Salesforce integration has also been an improvement, letting non-engineering teams work independently and freeing up engineering time.

Empower teams with critical insights

Companies new to usage-based pricing increasingly realize the power of real-time spend data to drive critical product and sales decisions. At AssemblyAI, the maturity of Metronome’s data export functionality came as a pleasant surprise. “Our entire company leverages the data. Our internal analytics team builds models to map customer spend, and every day, people are looking at how much certain customers are spending.” This data is now a critical tool for their team, supporting customer renegotiations and product decisions by providing clear insights into current rates and consumption patterns.

Tips for evaluating a billing system

Having gone through two billing migrations, Mary Pat summarizes the following guiding principles for selecting a billing system:

• Crystalize your business’s use case. Understand your customer segments and their billing needs—whether prepaid, postpaid, or PAYGO—and ensure the system can handle those requirements while protecting your business from fraudulent behaviors.
• Understand the level of scale the vendor can support. Assess the vendor's current capacity and roadmap to confirm they can support your growth trajectory. Check their critical service-level agreements (SLA), such as invoice compute throughput and alert latency. A misalignment here can derail your scaling efforts.
• Prioritize transparency and customer experience. Look for tools that provide real-time spend tracking, configurable alerts, and intuitive dashboards to elevate customer trust and satisfaction.
• Check financial stability. Ensure the vendor is financially secure, reliable, and equipped to meet the critical needs of your company's growth.
• Know their support SLAs. Confirm the vendor’s SLA for response time, reliability, and issue resolution. A responsive support team is key to future-proofing your billing operations.

By following these principles, you’ll be better equipped to choose a billing partner that aligns with your goals and can grow with your business.

If you’re interested in learning more about Metronome and how we can support your billing needs, you can contact us here.