Yes, all packets from a TCP connection will keep going to the backend that was chosen when the connection first came in. This is preserved even if other backends are added and removed to the set of eligible targets. It's also preserved even if the backend itself becomes unhealthy, but the connection seems not to be impacted. For example, if the backend application stops listening for new connections - existing ones will continue to work.
We try really really hard to preserve connections and the system is designed to keep connections healthy even for months and years.
We try really really hard to preserve connections and the system is designed to keep connections healthy even for months and years.