Elastic Load Balancer

Target 5XX errors v.s. ELB 5XX errors

Internet -> ELB -> Target
Internet <- ELB <- Target

Target 5XX means it’s the BE returning 5XX errors.

ELB 5XX means it’s the ELB returning 5XX errors.

ELB 502 error v.s. ELB 504 error

502 Bad Gateway

Unable to connect to Target / BE

504 Gateway Timeout

Connected to Target / BE but BE is taking too long to response