Techniques are described for facilitating flow symmetry using a scalable service platform that anchors the service chain. The scalable service platform may facilitate flow symmetry and, at least in some cases, flow stickiness for a first packet flow (a “forward packet flow”) and a second, related packet flow (a “reverse packet flow”) both traversing the service chain in the forward and reverse directions, respectively. For example, a virtualized computing infrastructure may deploy a scalable service platform to perform load balancing of multiple forward packet flows, received from the gateway, among multiple parallel service instances for an ingress service in a service chain. For each corresponding reverse packet flows for the multiple forward packet flows, the scalable service platform load balances the reverse packet flow to the service instance for the egress service in the service chain that is applied to the corresponding forward packet flow.