Status: IN
Metrics achieves complete write-read structural separation: the write path uses frozen tag sets as immutable hash-safe keys with bisect insertion maintaining sorted temporal order, while the read path provides flexible subset matching for partial-tag queries and two-tier downsampling for bounded historical access — neither path compromises the other's invariants.
write-path immutability and read-path flexibility are independently maintained
Depends on (SL): metrics-indexing-separates-write-key-from-read-matching, metrics-sorted-invariant-survives-downsampling