chore(351): add service reliability standard

[oluashiruHO]

Is this pull request a content or a code change? (Please fill in the relevant section and delete the other)

Code change

I can confirm:

Accessibility considerations

• [x] Please review the accessibility checks for layout changes.
• [x] This change will not change layouts, page structures or anything else that might impact accessibility

Content change

• [x] Please review the accessibility checks for content changes.

I can confirm:

• [x] Content does not include any code or configuration changes (excluding frontmatter information)
• [x] Content meets the content standards e.g. Writing a principle and Writing a standard
• [x] Content is suitable to open source, i.e.:
  • Content does not relate to unreleased gov policy
  • Content does not refer to anti-fraud mechanisms
  • Content does not include sensitive business logic
• [x] Last updated date for content is correct

[daniel-ac-martin]

I wonder whether this is really a single standard. (I defer to others on the definitions we are using.)

To me 'service reliability' is a goal that we are trying to achieve, rather than a specific standard. So I wonder if this should be broken down.

I also think this assumes that every service has a high availability requirement, which isn't really true. If we were to consider a back-end process (no human user), how many of these points remain as MUSTs?

[robertdeniszczyc2]

Hi,

I started providing feedback on this in the PR, but I think a lot of my thoughts are already captured by @daniel-ac-martin above (https://github.com/UKHomeOffice/engineering-guidance-and-standards/pull/352#issuecomment-1824850240).

Service reliability is already mentioned in the MaC Pattern and I feel some of the MUSTs in this feel closer to a Pattern than a Standard.

I'm happy to talk through in more detail, but I feel this needs some more refinement if it is to be implemented as a Standard.

Thanks, Rob