We utilize Datadog to monitor both some legacy products and a new PaaS solution that we are building out here at Icario which is Micro-Service arch.
All of our infrastructure is in AWS with very few legacies being rackspace. For the PaaS we mainly just utilize the K8s Orchestrator which implements the APM libraries into services deployed there as well as giving us infra info regarding the cluster.
For legacies, we mainly just utilize the Agent or the AWS integration. With APM in specific places. We monitor mainly prod in Legacy and the full scope in the PaaS for now.