# X_CACHE_JITTER_INVALID

## Means

a TTL jitter fraction outside `[0, 1)`

## Typical cause

`cache.<tier>.jitterFraction` at `1` or above, negative, or not finite. Jitter exists because 40,000 keys warmed by one rolling restart share one TTL and therefore one expiry instant, and spreading them is the only thing that stops the herd — a fraction of `1` shaves a whole lease away, a negative one **extends** it past what the caller asked for. Both are miswiring rather than preference, refused where the TTL rule already lives

## Fix

set `cache.<tier>.jitterFraction` in `app.config.ts` to a value in `[0, 1)` — `0.05` is the default, `0` disables jitter

[Cache](/error-codes#cache)