When one of the co-creators of the popular open-source stream processing framework Apache Flink launches a new startup, it's worth keeping an eye on. Stephan Ewen joined the founding team of the open-source project in 2010 and later became CTO of Data Artisans, which aimed to monetize Flink before Alibaba acquired the company in 2019 and rebranded it as Ververica. After the requisite three years there, Ewen launched workflow-as-code startup Restate with Flink committers and former Data Artisan/Ververica colleagues Igal Shilman and Till Rohrmann.
Restate, whose overall mission is to make distributed application development easier, today announced that it has closed a $7 million seed round of funding, reached version 1.0 of its open BSL licensed version, and launched its managed cloud services.
What's great about Restate is that it's so fast and lightweight that developers can use it where traditional workflow systems are too slow and resource intensive. It's backed by a durable execution engine that allows you to set up fault-tolerant communication between services and processes, and it's integrated with Function-as-a-Service platforms like AWS Lambda and Cloudflare Workers. It's ideal for microservices architectures, but developers can also use it for task queues, event processing, and service orchestration in systems like inventory management and reservations.
It's worth noting, however, that Restate isn't the first to adopt the concept: open-source platform Temporal, for example, offers a somewhat similar feature set, though the Restate team would argue that their system is faster and more lightweight.
Ewen said that after 13 years with Flink, it was time to tackle a new problem. “While we were working on Flink, a series of use cases kept coming up, which were people abusing Flink for transaction orchestration-style use cases,” he told me. “They weren't doing very well when they used Flink for that, but they were saying they couldn't find anything else.”
After seeing users repeat this over and over again, the team decided that if they were to start another company, they would look at how to solve this problem more elegantly.
Nearly every modern application today consists of a chain of workflows handled by a set of distributed services that need to communicate reliably with each other. Building such fault-tolerant distributed systems requires highly experienced teams (many companies build their own), but this is a minimum requirement and does not necessarily help companies differentiate their products.
Image credit: Restate
Seeing this, Ewen told me that the team took some of the stream-based processing ideas from Flink and combined them with the concept of workflows-as-code and specialized event logging, since logging is at the core of every workflow engine. “Restate took the workflow-as-code idea and added some other ideas inspired by stream processing. We evolved it into a more generic distributed programming model based on durable executions, virtual objects, and durable promises, and we put it on an event-driven foundation,” Ewen said.
The engine that powers it is very small and lightweight – Ewen emphasized that it even ships as a single binary and is fast – and they believe this will allow the service to be used in situations where you wouldn't traditionally use a workflow engine (such as e-commerce shopping carts). A lightweight workflow engine has built-in guarantees, perpetual execution, and the ability to retry if something goes wrong, for example ensuring that items in an abandoned shopping cart are returned to another customer after a certain amount of time, minimizing the risk that something will fail in the process.
“[Restate] “It's a very lightweight foundation that runs traditional workflow code and goes a little further than standard workflow use cases. It incorporates communication and state management as core concepts, so you can use it to build things that might not be a good fit for workflow but are very suitable if you want to build a proper microservices architecture,” Ewen explained.
The company also launched early access to its hosted Restate Cloud today. It's available for free for now, and Ewen was candid about the team's work to figure out how users will use it before deciding how to monetize the service.
The company's funding round was led by Redpoint Ventures, with participation from angel investors including Essence VC, firstminute.capital, Datadog founder Oli Pomel, and Apache Kafka and Confluent founders Jay Kreps and Neha Narkhede. The company plans to use the funding to hire talent, build out infrastructure, and offer SDKs for more languages (currently supporting TypeScript, Java, and Kotlin).
“Making distributed transactional applications correct, resilient, and scalable remains a challenge,” Kreps said. “Restate's approach, which combines durable execution with an event-driven architecture, is a big step toward solving this problem.”