Sizl: How we became the tech partner for the Chicago-based Dark Kitchen Network

This is the story of how to create a dark kitchen app for a fast-growing network offering food delivery and pickup in Chicago. It started with a complete rebuild of the existing platform and evolved into ongoing development of new features.

The product helped the company secure funding right after launch, and the company has continued to rapidly expand its coverage throughout the city. We're still actively involved in the development process, adding new features and ensuring the application runs smoothly and reliably.

Dark kitchens are one of the fastest-growing segments in food tech. These are professional kitchen spaces without dine-in areas, designed exclusively for fast, streamlined delivery.

For customers, this means getting meals delivered in as little as 20-30 minutes. For businesses, the dark kitchen business model enables faster scaling, greater cost-efficiency, and the flexibility to quickly adapt to shifting demand. Kitchens are "dark" because they're not open to customers. Such apps allow users to order food online for delivery, without being able to walk into the restaurant.

According to Statista,the global dark kitchen market has already reached $58.61 billion, and by 2030, dark kitchens could account for up to 50% of the food delivery and drive-thru market.

The first version of the Sizl app was built using Kotlin Multiplatform, a powerful but relatively uncommon technology that still lacks widespread library and package support. The change in CTOs also increased potential risks to product growth, including long-term maintainability, feature scalability, and quick iteration.

Our team was brought in to take on the challenge. Here's what we did:

• Rebuilt the entire dark kitchen app in React Native for better maintainability and faster feature deployment;
• Added two major features – Pick-up (for customer self-service orders) and Event Kitchen (for catering special event orders);
• Integrated analytics tools to provide visibility into user behavior and performance;
• Organized consistent design system;
• Adapted the platform to support multiple kitchen workflows, improving operational flexibility and conversion rates.

A few weeks after the new release, the Sizl team pitched the product to investors and successfully raised a seed round:

• $3,6 M

  total fundings

• $12 M

  post-money evaluation

We knew Alexey, Sizl's co-founder, before the project started. We interviewed him and planned to invite him to a roundtable discussion on food tech trends. Alexey had already successfully launched a large chain of Local Kitchen dark kitchens in a different region. His new project, Sizl, was developing quickly in the US market, but it encountered technical difficulties that could slow growth.

Looking for a team to rebuild Sizl, Alexey turned to our CEO, Maxim, for a recommendation. Since we had the necessary experience, food tech expertise, and technology stack, we agreed on terms and began developing Sizl.

The beginning of development.

The Sizl team provided us with a fully functional backend and supporting documentation. Some background processes needed clarification, so we worked closely with the client to build a dark kitchen app.

From the beginning, the focus was on iOS, as the US market is primarily focused on this platform. We also completely reworked the design, because the initial version did not accurately reflect the app's actual functionality.

We gathered a team of three mobile developers to work on the project. One developer took care of the main tasks, while the other two joined us as needed. The team worked together on the main scope (menu and cart), which helped us consolidate all the expertise and knowledge on the project.

We organized the process according to Agile principles. First, we divided the functionality into four key epics: menu, authorization, cart, and support. Then, we broke them down further and prioritized them as user stories.

First, we rewrote the main user journey, from choosing a dish to placing an order. Other scenarios (such as password recovery or contacting support) were implemented later.

This approach helped speed up development and eliminate unnecessary steps. For example, we postponed editing the profile – the user can enter all the necessary contact information when placing an order.

In addition, by tracking story points, we knew exactly how much time was being spent on tasks of different sizes. This allowed us to regularly stay ahead of schedule and complete fixtures faster than planned.

Work on the application began with a complete redesign. There was no consistency between the mockups and the actual functionality: the interfaces in Figma often didn't match what the app had.

We updated the current screens and added missing states for checkout and display of the dark kitchen schedule, organized a full-fledged design system, and worked out the UX for two new features: self-checkout and event ordering.

We also created a guide for the dark kitchen marketing team on how to work with banners: we specified requirements for aspect ratio, text protection fields, and described complex cases where graphics and text are used together. See more of our UI/UX design cases here.

Let's take a look at the basic user flow, integrations with third-party services and ready-made solutions, as well as special features that make Sizl different from other dark kitchens.

Previously, users had to register to access the menu, and the onboarding was complicated and overwhelming. We've simplified the process: with the "Explore Sizl" feature, customers can now browse the menu and explore popular items that are likely to be available at all stations.

It is not possible to place an order in guest mode. Users must choose the "Select delivery mode" option. At the same time, the delivery address can be specified even before registration, and after logging into the account it will be automatically retrieved and synchronized with the created account.

There are two options available to the user for receiving the order – Delivery and Pickup. When selecting delivery, the system automatically calculates the approximate time based on the address provided and displays it at the top of the screen.

If the kitchen is already closed, the user will see this even before placing the order. He can also immediately switch to self-delivery mode and choose which address to pick up the purchase.

To track how users download the app, we implemented scanning QR codes that contain links to UTM tags. A user is redirected to the App Store and downloads the app.

Here we use the Branch.io service to record the moment when the user clicks on the link and match it with the ID that appeared in the system after installation.

Then all the data from Branch.io is transferred to the Amplitude service, which is integrated with Meta Advertising Offices. This allows to track conversions across campaigns and understand exactly which channels are performing best. You can find more analytics collection tools we use in this article.

The menu is organized like a constructor: all dishes are grouped by categories called "shelves". For example, "Popular", "Breakfast", "Soups" and others. If the kitchen is temporarily out of service, the user will see a banner with a notification.

For some dishes there is a flexible customization. First, the user chooses the base, then adds additional ingredients, each of which affects the final cost. The system also offers upselling options, such as sauces, toppings, and other dishes that complement the main order.

Once all the dishes have been added to the cart, the user has a few steps to go to checkout. In the US, it is common to leave orders at the door, so we have provided a separate field for comments and delivery requests.

Name and phone number are automatically taken from the account settings. Next, user needs to select the delivery mode: standard (no price is specified) or priority – with expedited delivery for $1. This is a little trick: in fact, both options are paid, but such a small difference in delivery motivates the user to choose the faster option, thereby increasing the average check. As a result, the customer gets a more convenient delivery format, and the business gets additional revenue.

Because the availability of dishes in the Dark Kitchens format can change instantly, we added an additional checkout step immediately after a user confirms an order. The system sends a request to the backend. If some items are unavailable, a pop-up will appear with a list of unavailable dishes.

Sometimes users forget to update their address during checkout. That's why we send a warning if the current location differs by more than 500 meters from the location specified in the order.

To pay for an order, a user needs to link a card to the Sizl app. We also organized integration with Apple Pay to make the process as fast as possible. Users can also pay for part of their order with bonuses accumulated through the loyalty program.

In addition, we've added a separate screen with animation so the user can see that the payment is in process. There is also a cashless tipping option with fixed percentages to choose from.

Once the payment has been received, the user returns to the screen with the status. A map with the courier's movement is also displayed here, which is updated in real time.

In case of pick-up, the "I'm here" button appears: the user should press it when he arrives at the station to pick up his order and even share his geolocation with the station.

From yoga in the parks to festivals and large conferences, Chicago hosts many events every day. Together with Sizl, we have developed a special option for ordering food for attendees.

Some of the meals can be paid for by the organizer as a welcome bonus. To place an additional order, an attendee simply scans a QR code and a special menu created for the event opens. All orders will be displayed in the pick-up section at checkout and the menu will be available until the end of the event.

The organizer, in turn, must prepare a pick-up area where couriers will deliver the orders. For logistical convenience, each order is assigned a unique number. This helps to determine exactly which order belongs to a particular attendee.

Menu management is organized through the admin panel. The manager in charge of the kitchen at a particular station can edit the filling of "shelves".

The administrator can also use filters to stimulate additional sales: when selecting the main dish, the user is automatically offered a drink that is most often ordered with it, based on analytical data.

It is also possible to remove dishes from the menu through the administration if some ingredients are out of stock, simply by setting the item to stop.

Frontend: React Native
Design: Figma
Additional services: Branch.io, Amplitude, Getstream.io, Sentry.io

The complete rebuild took 2.5 months. The menu and authorization modules were the quickest to rewrite. Most of the time was spent on the shopping cart logic. Another month was spent on full testing and debugging.

Now we are actively developing the product and working on a separate application for drivers. Implementing new features takes an average of 1-2 days. For a fast-growing company like Sizl, speed is critical. The company aims to reach a wide audience and optimize delivery costs, which directly affects revenue.

We are constantly looking for bottlenecks in the system and thinking through scenarios in which the application can best serve the needs of both the darkkitchens network and its users. All while minimizing the impact on the company's operational processes.

• 3,5

  months