| Status | Complete |
|---|---|
| Impact | High |
| Driver/s | @Julian |
| Approver/s | @Everyone |
| Date | 30/08/2025 |
| Links | Links to relevant research, pages, meetings, and related decisions |
Background
Our choice for backend language was shaped by three key requirements: familiarity, popularity, and performance.
Choosing a language the team is more familiar with (or has a shallow learning curve):
- Minimises time spent learning syntax and language features
- Permits better programming practice through established language knowledge
Choosing a language that is popular for the application is important to:
- Maximise the number of available resources for developing robust and proven software
- Increase the amount of tooling and developer libraries available
- Reduces time spent “re-inventing the wheel”
Choosing an inherently performant language for the application is important for later stages of development when testing user experience, where higher level or domain-unoptimised languages may introduce delays that reduce software quality and UX.
Relevant Data
Add any data or feedback the team should consider when making this decision.
Options Considered
Typescript + Node
Positives:
- Very widely used for writing API servers
- Simple language
- Moderate (compile-time) type safety Negatives:
- Potentially un-intuitive runtime (using express for HTTP server)
- Half of team would have to learn Javascript/Typescript
Rust + Axum
Positives:
- Extremely fast
- Completely enforced type (and memory) safety
- Minimal memory footprint, can be deployed anywhere Negatives:
- Not as well supported as Node or Bun
- Most of team isn’t familiar with Rust (which has quite a high learning curve)
- Lower level than Typescript, sacrifice development time for performance and safety
Typescript + Bun
Positives:
- Very performant
- Rapidly growing support
- Cross-compatibility with Node
- Very simple runtime, servers are built with high-level ready-made library interfaces Negatives:
- Half of team would have to learn Javascript/Typescript
Action items
Add action items to close the loop on open questions or concerns.
Outcome
We have decided to use the Bun runtime with Typescript.