How Sunday used OTPs to grow user engagement with Prelude

Sunday is a comprehensive checkout solution that enhances the dining experience by integrating payment, ordering, menu management, reputation management, tipping and loyalty programs. Founded by former hospitality professionals, Sunday aims to help restaurants and their customers save time and streamline interactions. With over 50M users annually, Sunday helps more than 2,000 restaurants to connect and engage with their guests.

Building guest engagement, one OTP at a time

As Sunday scaled its operations, ensuring high service availability and resilience during peak demand became a top priority. The team needed an authentication solution that could handle global OTP messages efficiently without requiring extensive support or complex implementation.

Sunday’s goal was to make OTP messages the backbone of their restaurants’ loyalty strategy. By verifying their phone number at a restaurant, guests could seamlessly join its loyalty program and access related benefits.

OTPs are integrated throughout the entire guest journey—from start to finish. For example, when guests view a restaurant’s menu, they are invited to join the loyalty program by entering their phone number, verified via an OTP message. Similarly, after paying their bill, guests can redeem loyalty points by verifying their number once more.

Given the critical role OTPs play in Sunday’s strategy, they needed a provider they could rely on.

While Sunday’s team was developing their new flows, they encountered growing frustrations with their SMS API provider. Prices were rising, and at the same time, they experienced a noticeable decline in service quality and support.

"When Twilio, our previous provider, increased their prices and restructured their support team, the service fell short of our expectations—costs were high, and support was lacking. We knew it was time to make a change" added Arnaud Lemaire, Sunday’s CTO.

Simplifying global user authentication with Prelude

After a swift integration process, Prelude now handles all of Sunday’s SMS traffic, ensuring seamless guest interactions at every stage.

Reaching customers globally

While Sunday operates across Europe and North America, the restaurants they work with have international guests. They needed a solution that could reliably send OTP messages to phone numbers from all around the globe.

Prelude’s API connects Sunday to over 30 local and global providers, offering access to more than 1,000 routes across 230 countries. Prelude also supports multiple channels, including WhatsApp, Viber, and RCS, ensuring guests can receive their messages even without roaming data. This guarantees that someone from Brazil enjoying a nice meal in Paris will always receive their OTP message on time.

“Deliverability is our top priority. Being in the hospitality business, we handle phone numbers from all over the world, as many of our customers are international and bring their local numbers—even from some rather exotic regions. Prelude meets our needs by offering reliable coverage across all these diverse geographical areas.”

Premium customer support at no extra cost

Sunday’s team has direct access to Prelude’s support through a dedicated Slack channel. Whenever a question or issue arises, they can quickly reach out and get a prompt response from Prelude. This helps Sunday minimizing downtime for their users while improving efficiency for their team.

At Prelude, we prioritize customer support. All of our clients receive premium support at no extra cost. Whether via Slack, email, or phone, our team is here to guide clients every step of the way—making their challenges our own.

"Our relationship with Prelude’s support team is incredibly smooth. We can Slack them whenever needed, and they’re always ready to help, keeping us on track," said Arnaud.

Sending SMS at lower prices

By switching from Twilio to Prelude, Sunday’s team achieved significant savings on their user verification budget.

Prelude connects Sunday to multiple routes, selecting the most cost-effective option for each OTP request. We negotiate pricing with providers on behalf of our clients, and because we don’t add margins to message costs, our routing is unbiased—always choosing the best route based on price and performance.

“With Prelude, we've completely transformed our messaging strategy. Now, we send OTPs worldwide effortlessly, with full visibility into deliverability and conversion rates. Prelude has truly helped us level up our B2C engagement program", concluded Arnaud.