How Shine built a brand new bank on GCP and Cloud Spanner

Editor’s note: Technology today lets companies of any size take on entire industries simply with an innovative business model plus digital distribution. Take Shine, a French startup whose platform helps freelancers manage their finances—and their administrative commitments. Here, Raphael Simon, Shine’s CTO and co-founder, talks about why Shine built a new bank on Google Cloud, and in particular Cloud Spanner. Read on to learn how the enterprise-grade database combines the best of relational database structure and non-relational database scale with—coming soon—synchronous replication across regions and continents with a 99.999% (five nines) availability SLA.

More and more people are deciding to take the plunge and start a freelance career. Some of them by choice, others out of necessity. One of their biggest pain points is dealing with administrative tasks. In some countries, especially in Europe, the administrative burden of being a freelancer is similar to what a company of 10 or more people deals with. A freelancer doesn’t necessarily have the time or skills to manage all this paperwork. So we are building a new bank for freelancers from the ground up that helps automate administrative tasks associated with their business.

Shine’s banking services and financial tools make it as easy to work as a freelancer as it is to work for a larger company. We deal with administrative tasks on behalf of the freelancer so that he or she can focus on their job: finding and wowing clients.

Building our infrastructure 

At the same time, it’s vital for us to optimize our resources so we can maximize the time we spend developing user-facing features. In our first six months, we iterated and validated a prototype app using Firebase, and secured our seed funding round (one of the largest in Europe in 2017).

Based on our positive experience with Firebase, plus the ease-of-use and attractive pricing that Google Cloud offered, we decided to build our platform on Google Cloud Platform (GCP). We were drawn to GCP because it has a simple, consistent interface that is easy to learn. We chose App Engine flexible environment with Google Cloud Endpoints for an auto-scaling microservices API. These helped us reduce the time, effort, and cost in terms of DevOps engineers, so we could invest more in developing features, while maintaining our agility. We use Cloud Identity and Access Management (Cloud IAM) to help control developer access to critical parts of the application such as customer bank account data. It was quite a relief to lean on a reliable partner like Google Cloud for this.

Database decisions 

Due to the sensitivity of our customers’ data, the stakes are high. We pay careful attention to data integrity and availability and only a relational database with support for ACID transactions (Atomicity, Consistency, Isolation, Durability) can meet this requirement.

At the same time, we wanted to focus on the app and user experience, not on database administration or scalability issues. We’re trying to build the best possible product for our users, and administering a database has no direct value for our customers. In other words, we wanted a managed service.

Cloud Spanner combines a globally distributed relational database service with ACID transactions, industry-standard SQL semantics, horizontal scaling, and high availability. Cloud Spanner provided additional security, high-availability, and disaster recovery features out-of-the-box that would have taken months for us to implement on our own. Oh, and no need to worry about performance -- Cloud Spanner is fast. Indeed, Cloud Spanner has been a real asset to the project, from the ease-of-use of creating an instance to scaling the database.

Cloud Spanner pro tips 

• The first connection to Cloud Spanner takes a long time to initialize, which makes it difficult to expose an API through Cloud Functions. Instead, we used App Engine flexible environment to build our microservices API for a serverless approach that has very good performance. We use Cloud Functions for simple asynchronous scripts for background tasks that do not require an immediate answer to the client (e.g., sending an iOS notification given the user parameters) that we trigger via Cloud Pub/Sub. 
• Cloud Spanner allows us to change a schema in production without downtime. We always use a NOT NULL constraint, because we generally think that using NULL leads to more errors in application code. We always use a default value when we create an entity through our APIs and we use Cloud Dataflow to set values when we change a schema (e.g., adding a field to an entity). 
• With microservices, it’s generally a good practice to make sure every service has its own database to ensure data isolation between the different services. However, we adopted a slightly different strategy to optimize our use of Cloud Spanner. We have an instance on which there are three databases—one for production, one for staging and one for testing our continuous integration (CI) pipeline. Each service has one or more interleaved tables that are isolated from others services’ tables (we do not use foreign-keys between tables from different services). This way our microservices data are not tightly “coupled”. 
• We created an internal query service that performs read-only queries to Cloud Spanner to generate a dashboard or do complex queries for analytics. It is the only service where we allow joins between tables across services. 
• We take advantage of Cloud Spanner’s scalability, and thus don’t delete any data that could one day be useful and/or profitable. 
• We store all of our business logs on Cloud Spanner, for example connection attempts to the application. We append the ‘-Logs’ suffix to them. 
• When possible, we always create an interleave. 

• It’s saved us weeks, if not months, of coding. 
• We feel we can rely on it since it’s been battle-tested by Google. 
• We can focus on building a disruptive financial services product for freelancers and SMBs.

Shine will launch in France this fall, and later throughout Europe. We have our sights set on the United States in the future too. To learn more about Shine, or talk about GCP or Cloud Spanner, feel free to reach out to us on Twitter.