Diablo 2, according to the team, was made for centralization. The downside of that means that only a single instance of this particular service can run at any time meaning they're unable to D2R Ladder Items offload some part of the workload to servers in regional locations.
"Importantly the service is a singleton, which implies that we will only be able to run one instance of it to ensure that everyone is seeing the most current and accurate games at all times," the devs wrote. "We improved this service in order to make it more modern technology, but as already mentioned, a lot of the issues we have come from the creation of games."
At present, there's a range of short-term solutions and plans to overhaul Diablo 2's design so that it's able to scale better for modern demand. The service that provides an inventory of games for players, for instance is now being restructured into a service that is its own.
The devs will also be introducing the login queue, similar to World of Warcraft, to avoid situations in which servers get overloaded when hundreds of thousands of game instances are launched all simultaneously:
To tackle this issue there are people working in a login queue just like the queue you experienced when playing World of Warcraft. This keeps the number of players within the limits we have at the time which allows us to track where the system is straining and take action before it brings the game to a complete stop.
Each time we solve an issue, we'll capable of increasing the number of limits. The login queue has been partially implemented in the backend (right now, it appears like a failed authentication on clients) and will be implemented in the next few days on PCs, with console to follow after.
Players also have the option of being rate restricted, but only in instances where games are being constructed, closed, and reconstructed over short durations D2R Ladder Items Buy, which is mostly instances where players are farming out areas like Shenk Eldritch or Pindleskin.