Serverless Architectures

Serverless is a hot topic in the software architecture world. We’re already seeing booksopen source frameworks, plenty of vendor products, and even a conference dedicated to the subject. But what is Serverless and why is (or isn’t) it worth considering? Through thisevolving publication I hope to enlighten you a little on these questions.

To start we’ll look at the ‘what’ of Serverless where I try to remain as neutral as I can about the benefits and drawbacks of the approach – we’ll look at those topics later.

What is Serverless?

Like many trends in software there’s no one clear view of what ‘Serverless’ is, and that isn’t helped by it really coming to mean two different but overlapping areas:

  1. Serverless was first used to describe applications that significantly or fully depend on 3rd party applications / services (‘in the cloud’) to manage server-side logic and state. These are typically ‘rich client’ applications (think single page web apps, or mobile apps) that use the vast ecosystem of cloud accessible databases (like Parse, Firebase), authentication services (Auth0, AWS Cognito), etc. These types of services have been previously described as ‘(Mobile) Backend as a Service’, and I’ll be using‘BaaS’ as a shorthand in the rest of this article.
  2. Serverless can also mean applications where some amount of server-side logic is still written by the application developer but unlike traditional architectures is run in stateless compute containers that are event-triggered, ephemeral (may only last for one invocation), and fully managed by a 3rd party. (Thanks to ThoughtWorks for their definition in their most recent Tech Radar.) One way to think of this is ‘Functions as a service / FaaS’ . AWS Lambda is one of the most popular implementations of FaaS at present, but there are others. I’ll be using ‘FaaS’ as a shorthand for this meaning of Serverless throughout the rest of this article.

Mostly I’m going to talk about the second of these areas because it is the one that is newer, has significant differences to how we typically think about technical architecture, and has been driving a lot of the hype around Serverless.

However these concepts are related and, in fact, converging. A good example is Auth0 – they started initially with BaaS ‘Authentication as a Service’, but with Auth0 Webtask they are entering the FaaS space.

Furthermore in many cases when developing a ‘BaaS shaped’ application, especially when developing a ‘rich’ web-based app as opposed to a mobile app, you’ll likely still need some amount of custom server side functionality. FaaS functions may be a good solution for this, especially if they are integrated to some extent with the BaaS services you’re using. Examples of such functionality include data validation (protecting against imposter clients) and compute-intensive processing (e.g. image or video manipulation.)