AWS Shield vs Let's Encrypt: What are the differences?

Developers describe AWS Shield as "Managed DDoS Protection". AWS Shield is a managed Distributed Denial of Service (DDoS) protection service that safeguards web applications running on AWS. AWS Shield provides always-on detection and automatic inline mitigations that minimize application downtime and latency, so there is no need to engage AWS Support to benefit from DDoS protection. On the other hand, Let's Encrypt is detailed as "A free, automated, and open Certificate Authority (CA)". Let’s Encrypt is a free, automated, and open certificate authority brought to you by the non-profit Internet Security Research Group (ISRG).

AWS Shield and Let's Encrypt can be primarily classified as "Security" tools.