Configuring Speed‑Aware Cache TTL for Railway Train Position Updates

The goal is to guarantee that the age of cached train‑position data never exceeds a distance‑based staleness limit derived from current speed, block length, and required reaction time, ensuring downstream signaling decisions rely on sufficiently fresh information.

Presently the cache uses a fixed 30‑second TTL with no documented mechanism to vary this timeout according to dynamic factors such as train speed, track gradient, or communication latency. This leaves unresolved whether and how the TTL should be adjusted, and what bounds should be applied to maintain safety under high‑speed operation.

Which dynamic parameters should influence the TTL, what functional form (e.g., linear, lookup table) should define the relationship, and what maximum permissible staleness (in seconds or distance) should be enforced for different speed regimes?