Rewrite _api to be more performant.

[TokenChingy]

Is your feature request related to a problem? Please describe.
Improve performance and handling of larger loads.

Describe the solution you'd like

1. Rewrite _api to be more performant.

Describe alternatives you've considered
N/A

Additional context
This will be done in a different branch and will be merged in when it works. I will continue working on _api as it is now and implement the final few features expect the following:

• Implement schema validation for updates — Ajv doesn't support partial validation.
• Implement GraphQL — No point when it's being rewritten.
• Implement an admin interface — No point when it's being rewritten.