Optimising serverless for BBC Online
Previously I talked about why Web Core, our new web technology platform is built using serverless cloud functions. In this post we’ll discuss our experience of integrating them with our architecture and how we’ve optimised them for our use case.
The BBC makes use of many different technology providers to deliver its online services. We make use of AWS’s Lambda service to deliver the serverless functionality for Web Core. There are other platforms which provide similar functionality, such as GCP’s Cloud Functions, Azure’s Functions, and Apache’s OpenWhisk. The majority of points made can be applied to any of these platforms.
We make use of serverless in two of the high CPU intensive areas of Web Core. The first is the React app that renders the HTML. This layer understands which visual components make up a page, and fetches the data for them. The second is our business logic layer, which transforms data from many different BBC systems into a common data model.
Unlike other typical architectures we don’t make use of an API gateway to launch our serverless functions. Instead we have our own custom APIs running on virtual machine instances. These sanitise requests, forward traffic to the relevant serverless functions as well as handling caching and fall backs. These APIs are high network, high memory, low CPU services. This best fits a virtual machine instance over a serverless approach due to the availability of different instance types. In addition the scaling pattern for the APIs is slower and more predictable as traffic grows, compared to the high CPU workload carried out by our serverless functions.
