Description

This issue tracks a possible future improvement to the way expired prebuilds are filtered in the system.
Currently, we use in-memory filtering to separate expired from running (non-expired) prebuilds when constructing the PresetSnapshot:

This approach is simple and performs well at the current scale. However, if the number of running prebuilds increases significantly, it may become a performance concern.

Context

• Database query GetRunningPrebuiltWorkspaces returns all running workspaces (non-expired and expired workspaces).
• A new slice Expired was added to PresetSnapshot, populated via in-memory filtering.
• We chose not to add a DB query yet to keep the implementation small and simple: feat: implement expiration policy logic for prebuilds #17996 (comment)

Potential Improvement:

• Introduce a dedicated database query to fetch expired workspaces.
• Update the current GetRunningPrebuiltWorkspaces database query to only return non-expired workspaces.
• This would avoid loading all running prebuilds into memory and manually filtering them.
• Likely to be more efficient at larger scale.

While in-memory filtering is sufficient for now, introducing a DB query helps future-proof the system and ensures consistent performance in larger on-prem installations.

Action Items

• Monitor performance as prebuild usage increases.
• Revisit this issue if:
  • Prebuild count grows significantly.
  • Memory usage or latency becomes a concern in prebuild snapshot construction.