No encryption key size, RSA included, has a black-and-white 'technical upper limit'.

That said, there are standards. For example, The NIST recommends a minimum RSA key length of 2048 bits.

• 4096-bit RSA is currently considered a secure key size for most applications (which is also backed by The NIST in that article).

• Key sizes beyond 4096 bits (such as 7680 or even 15360 bits) may still be technically possible, but are often seen as overkill for most current use cases.

  The increased key length does provide more security (potentially against future threats such as quantum computing), but it also introduces significant performance overhead.