For most small engineering teams, offering phone numbers in four countries would be a multi-quarter infrastructure project. For Zernio, it is a query parameter. "Creating a phone number in Spain or a phone number in Germany is basically an API call with just a new filter," said Pau Guirao, a developer at Zernio. "We can add a new country by adding just a new filter on the API."
Zernio, an eight-person bootstrapped company headquartered in Girona, Spain, and known until recently as Late, builds a social media and messaging API that lets developers and AI agents publish, message, advertise, and talk to customers across 16 channels. When the team expanded into the communications and telecom layer, it needed depth it could not build alone. "On this type of product, you need WhatsApp, SMS, calling, voice. There's a lot of different and super deep products," Guirao said. "We chose Telnyx because Telnyx offers all of those from scratch, and everything is built into the API, which is super easy for us to integrate."
Depth on demand for a three-developer team
Zernio's entire communications product is maintained by a handful of engineers, which makes the shape of the underlying API a business decision. "It's super easy for a small team like us, with two or three developers, to quickly develop any product that you want," Guirao said. "The API goes as deep as you want. Any feature that's missing from your product, you go into the Telnyx docs and the product is already built on top of the API."
That depth turned phone numbers into something Zernio could sell as a product in its own right. The team provisions numbers in Spain, Brazil, the United States, and Germany without touching carrier relationships in any of them. "Handling all of that phone provisioning is super hard building it from scratch," Guirao said. Now it is the part of the stack he thinks about least.
Months of 10DLC work, reduced to a few API calls
The clearest before-and-after came with US messaging compliance. Zernio had scoped what it would take to implement 10DLC provisioning on its own. "It's a super hard product to implement from scratch. We've been looking into it," Guirao said. "Implementing that entire flow via API on Telnyx was super easy. The product went from being months of integration to just a few API calls. Everything is handled on Telnyx, and it let us focus more on the product than the infrastructure. It's a win-win for both."
The same logic applies across borders, where each new market brings its own regulatory processes. "Serving all those customers in all those different countries means we have to follow a real set of regulatory processes, and it's hard to handle all of that," Guirao said. "With Telnyx, all of that is handled on their side, on their infrastructure. For us, it's super easy to maintain all those customers."
Growth measured in phone lines, messages, and revenue
The numbers have followed. "Last month we provisioned two or three thousand phone lines. We're sending 80,000 SMS and around 10 to 12 thousand calls," Guirao said. "Our product is quickly expanding and it's increasing our revenue each month." The company now counts roughly 500 customers across EMEA alone. "Pretty big for us," he said.
A recommendation built on ease of integration
Asked to make the case for Telnyx, Guirao returned to the property that shaped everything else Zernio built. "I would recommend it because it's really easy to integrate. Everything, at least for us, is built on top of an API," he said. "Any product that you want, you can quickly develop. Super simple.
