ycb_valkey_cba5854636996

what a new run launched now would send

Clients need to atomically set multiple string keys and apply one shared expiration (and optional NX/XX) in a single command, instead of pairing MSET with a separate EXPIRE (or looping SET). Add that command so it behaves like MSET for the values, with SET-style expiration/condition options applied to every key in the call.

Syntax:
  MSETEX numkeys key value [key value ...] [NX | XX]
      [EX seconds | PX milliseconds |
       EXAT seconds-timestamp | PXAT milliseconds-timestamp | KEEPTTL]

Options (same meanings as SET):
- EX / PX — relative TTL in seconds / milliseconds
- EXAT / PXAT — absolute Unix expiry in seconds / milliseconds
- KEEPTTL — keep existing TTLs on the keys being set
- NX — set only if none of the keys already exist
- XX — set only if all of the keys already exist

Returns: integer 1 if all keys were set; 0 if NX/XX blocked the write (and no keys were modified). Reject invalid numkeys, arity/syntax, conflicting options, and invalid expire values consistently with existing string commands. Follow existing server conventions for expire handling, replica propagation of absolute expiry, keyspace notifications, and COMMAND GETKEYS metadata for the new command.

Interface contract — the change must expose exactly this surface:
Public command name must be MSETEX (lowercase msetex in the protocol), registered so COMMAND GETKEYS / GETKEYSANDFLAGS work; callable as: MSETEX <numkeys> <key> <value> [<key> <value> ...] [NX|XX] [EX <sec>|PX <ms>|EXAT <sec-ts>|PXAT <ms-ts>|KEEPTTL]; reply is integer 0 or 1.

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