Connections between your sandboxes are no longer reset in bursts

Connections by name (<name>.sandbox.internal) were refused past 100 new connections a second across the whole account, so a sandbox opening several at once saw some of them reset (about 17% with 8 at once). The limit is now 1,000 a second per account and 500 a second per target sandbox, and a connection over it waits for its turn instead of being refused. A sandbox created moments ago is also reachable within about a second; before, it could be refused with private-network-off or private-network-no-sandbox for up to 15 seconds. See networking.