Constant INDEX_MAX 

pub const INDEX_MAX: u64 = _; // 18_446_744_073_709_551_614u64

The largest index an array will accept.

Redis reserves UINT64_MAX as “no insert has happened yet” in the cursor that ARINSERT and ARNEXT share, so it is not a position anything can be written to, and ARSET k 18446744073709551615 v is an error rather than a write. Keeping the same ceiling here keeps that cursor able to mean the same thing when it lands.