String sizes are limited to 256MB. Indices (say in GETRANGE and SETRANGE commands) should be signed 32 bit integers in range [-2147483647, 2147483648].
SORT does not take any locale into account.
EXPIRE, PEXPIRE, EXPIREAT and PEXPIREAT accept NX together with GT or LT: the expiry is set when the key has none, otherwise GT or LT alone decides. Redis rejects these combinations as incompatible.
Expirations are limited to 8 years. For commands with millisecond precision like PEXPIRE or PSETEX, expirations greater than 2^28ms are quietly rounded to the nearest second losing precision of less than 0.001%.
We use lua 5.4.4 that has been released in 2022. That means we also support lua integers.