Select the length of the encryption key: 1024 bit or 2048 bit.
A 1024-bit encryption key places a smaller load on the CPU, but it is considered obsolete because it cannot provide reliable encryption due to its technical specifications. Also, the existing hardware probably will turn out to be incompatible with SSL certificates featuring 1024-bit keys.
A 2048-bit encryption key meets all state-of-the-art encryption standards. However, use of a 2048-bit encryption key may add to the load on a CPU.