Answer by Sergey Ponomarev for Store key in compact form

You can try Elliptic Curve (ECC) keys which are mush smaller:

openssl genpkey -out small.pem.p8

The size of the PEM key is 119 bytes

You can also output to a raw DER form:

openssl genpkey -out small.der.p8 -algorithm ed25519 -outform DER

Now it's size is only 48 bytes. And it contains internally it's public key.