Local NodeJs https overhead

There is API end-point in my local NodeJS development that should works via https.

I generated private key and self-signed certificate:

1. openssl genrsa -out cert.key 2048
2. openssl req -new -key cert.key -out cert.csr
3. openssl x509 -req -days 3650 -in cert.csr -signkey cert.key -out cert.crt

and added them to options:

const options = {  key: fs.readFileSync('cert.key'),  cert: fs.readFileSync('cert.crt'),  ciphers: ... <-cipher suite};https.createServer(options, (req, res) => {...}

It works, but too many requests to the end-point lead to excessive load.

Can low private key size or some simple cipher suite reduce the overhead?