For information on how to renew certs on 57North core services, see here.
Let's Encrypt is a certificate authority that launched on April 12, 2016 that provides free X.509 certificates for Transport Layer Security (TLS) encryption via an automated process designed to eliminate the current complex process of manual creation, validation, signing, installation, and renewal of certificates for secure websites. 57North uses Let's Encrypt for a number of services.