AA set of Kubernetes controllers that deliver applications from Git using GitOps
BA container runtime that schedules and runs Pods on Kubernetes nodes
CA CI service that builds images and runs tests when code is pushed
DA service mesh that manages traffic and mTLS between Kubernetes services
Why this is the answer
Flux is a GitOps CD toolkit — controllers that reconcile a cluster to Git. Not a container runtime (that's containerd), not a CI build service, and not a service mesh.