I have developed my DRF back-end API locally, deployed it on an AWS Lightsail instance (with a public static IP) and I now want to secure it with HTTPS.
I understand that in order to use Let's Encrypt (and not pay for an SSL certificate), I have to have a domain name associated to my instance IP since Let's Encrypt doesn't provide certificates for public IPs. As this is my back-end API (and not just a website), I don't intend to buy a domain specifically for this.
Can I, somehow, associate my Lightsail IP with another domain that I've already purchased (and is used to host my company's landing page)? If yes, will there be any impact on my API's performance?
Is there any other alternative to obtain an SSL? (Apart from paying another CA to issue this for my public IP?)