TOUCHCount how many of the given keys exist.
| 语法 | TOUCH key [key ...] |
| 分组 | generic |
| 参数个数 | -2 |
| 起始版本 | 1.0.0 |
| 标志 | readonly |
| 复杂度 | O(N) keys — one existence probe per key on its owning shard |
| Redis 兼容性 | differs: kevy has no idle-time clock to reset, so TOUCH is EXISTS with the eviction bookkeeping the probe already does |