Currently, batching RPC requests across wallets does not work due to the fact that each wallet has its own endpoint. This results in relatively slow processing speed if a client queries multiple wallets.

See discussion in #18453 (this and this).

There are probably multiple approaches how to improve that:

• The foreachwallet RPC meta call that takes the actual call/arguments as parameters.
• A /foreachwallet http endpoint
• Add allwalletsXXX rpc calls (like getallwalletsbalance or getwalletsbalance
• ... (more?)