Repsol Scales Waylet to 10 Million Users

THE CHALLENGE

Scaling a digital ecosystem without limits

In the fast-moving world of digital mobility, consumer expectations are high. Whether paying for fuel at the pump, managing an electric vehicle charging session, or checking home electricity consumption, users demand instant responsiveness. For Klikin, the software company behind Repsol’s flagship app, Waylet, meeting these demands requires an engineering culture of autonomy and a database platform that scales effortlessly.

Based in Spain, Klikin operates with the agility of a startup despite being a subsidiary of energy multinational Repsol. When Repsol acquired a majority stake in Klikin in 2017, Waylet was a modest application with approximately 40,000 registered users handling around 5,000 payment transactions a day. But the vision was big.

The company’s strategic plan was to create a comprehensive, easy-to-use, package of energy solutions that would incentivize customer loyalty by offering increasingly greater benefits based on the number of services a user has with Repsol.

“Our role was to materialize those changes and make them a reality,” said Bálder Carraté, Principal Software Engineer, Klikin.  Waylet, thus evolved from a simple mobile payment tool into a comprehensive ‘super app,’ that allows users to pay for fuel, charging, carwashes, and utility contracts and with each payment earn variable cashback rewards which can be used in future transactions.

This evolution presented a twofold challenge: scale and complexity. Successfully meeting a gap in the market, combined with an attractive cashback incentive—and  rewards increasing in line with the number of Repsol services used—meant Waylet’s user base was growing rapidly. It was also experiencing clear seasonal peaks in service station refueling when traffic could double, sometimes even triple. At the start of a long bank holiday weekend, or change of fortnight in summer, queries could surge from a baseline of around 6,000 to 12,000 per second.  Meanwhile, a delay of even a few seconds at a payment terminal could lead to queues at service stations and damage the brand’s reputation.

Simultaneously, the data model needed to evolve rapidly. Integrating home energy management meant processing high-volume meter readings and consumption profiles, fundamentally different data types from transactional payments. Klikin needed a database architecture that could support this exponential growth and diverse feature set without forcing its engineering team to become full-time database administrators.

To secure this flexibility and effortless scale, Klikin built its future on MongoDB Atlas.

OUR SOLUTION

Building a cloud-native foundation on MongoDB Atlas

Recognizing that a rigid relational database would stifle its rapid iteration cycles, Klikin chose MongoDB for its document-oriented flexibility and eventually migrated the entire backend to MongoDB Atlas to adopt a fully managed, cloud-native developer data platform. “Achieving the agility and development speed that drives Waylet’s success would have been impossible with a relational database or an on-premises model,” said Carraté. “That flexibility has been a decisive factor in our evolution.”

Today, MongoDB Atlas serves as the backbone for every core element of the Waylet ecosystem—users, products, transactions, and session data all read and written through the platform. The move to a managed service was strategic, allowing Klikin’s developers to maintain full autonomy.

“We’re pragmatic. We didn't have an expert database administrator, nor did we think it would bring us value to shoulder that burden,” says Carraté. “The managed capabilities of MongoDB Atlas fit very well with our needs—that’s something we value very, very much.”

The flexibility of the document model allowed the team to adapt to new business requirements without costly migrations. When Repsol introduced home energy management features to handle complex electricity contracts, the team chose MongoDB Time Series collections. This allows Klikin to break down household consumption data into granular insights, showing users precisely how much they have spent on categories such as heating, air conditioning, and kitchen appliances.

Furthermore, with MongoDB’s multi-cloud and multi-region capabilities, Klikin has ensured that as it expands geographically—most recently into Portugal with the MyRepsol app—its infrastructure can be replicated and localized with minimal friction. “MongoDB allows us to start a project in a country with agility, with security, and with confidence,” said Carraté. “And that’s very important.”

OUTCOME

Uninterrupted growth and a 4.8-star experience

Today, Waylet is one of the most popular consumer apps in Spain, maintaining an exceptional 4.8-star rating across both the Apple App Store and Google Play Store—a rarity for utility and payment applications.

Powered by MongoDB Atlas, the platform has scaled seamlessly from its humble beginnings to support over 10 million registered users, and the numbers reflect a transformation defined by both speed and stability. The system now processes between 300,000 and 350,000 daily payment transactions—a staggering 6,900% increase—and can handle peaks of over 10,000 queries per second while maintaining a read latency of just 0.2 milliseconds.

The platform's stability has been absolute. “In eight years of a production system with high traffic, there hasn't been a single stumbling block,” noted Carraté. “That is something quite remarkable.”

Beyond raw performance, the move to MongoDB Atlas has unlocked profound operational efficiencies. A lean engineering team now manages approximately 2 TB of storage across nearly 300 collections without the need for dedicated database administrators—proving that massive scale doesn't require massive overhead. This architectural agility has also fueled rapid innovation, enabling Klikin to replicate its success across borders with the swift launch of the ‘MyRepsol’ app in Portugal, running on an independent yet identical MongoDB stack.

Looking ahead, Klikin is continuing its tradition of adopting cutting-edge features to enhance security and user experience, and has just launched a project that features Atlas Stream Processing.

“It’s hard for me to imagine how we could have done all this with another solution,” said Carraté. “MongoDB has accompanied us throughout this evolution, allowing us to scale progressively over time and handle seasonal peaks, with 100% reliability and perfect availability. It seems that we chose the right tools!”