Deployment standards

We use Docker containers for delivery of all bespoke software being deployed to AWS and Azure

Where we develop bespoke software, we default to using a Docker container as the deployable item.

Unless the technology does not support containerisation, all deviations from this standard will be treated as architectural exceptions.

Rationale

Containerisation is most applicable to certain specific scenarios, such as highly-available applications with varying demand or when using technologies that have a frequent update cycle.

However, running and managing a delivery pipeline and operational environment that supports both containers and more traditional virtual machines results in a duplication of effort and technical solutions.

Therefore, we will seek to minimise or eliminate this duplication by always preferring containerisation.

Containerisation also allows us to better manage a diverse application estate as it somewhat mitigates the need for across the board standardisation and large, coordinated upgrade projects, allowing instead for more nuanced decision-making.

We deploy code rather than containers to AWS Lambda and Azure Functions where their use is formally justified

There are cases where it will make sense to use a serverless platform rather than a containerised solution, but these must be individually justified and recorded as formal architectural decisions.

Additionally, justifications for using serverless platforms can only be considered for Javascript or C# functions.

Rationale

Serverless platforms provide a greatly reduced operational burden, but are not so well represented in development and have certain limitations that can make their use inappropriate. They also represent some vendor lock-in that, whilst minimal, is still not preferred.

We regularly review our use of serverless platforms

In particular, we will ensure that: - Vendor lock-in doesn't increase - We identify opportunities to rationalise these standards to use, effectively, "serverless containers"

Rationale

As serverless platforms are still relatively immature, we will need to ensure that our standards are still appropriate.