curl --request POST \
  --url https://api.example.com/broadcast_tx_async \
  --header 'Content-Type: application/json' \
  --data '
{
  "params": {
    "signed_tx_base64": "aSDinaTvuI8gbWludGxpZnk=",
    "wait_until": "EXECUTED_OPTIMISTIC"
  },
  "id": "dontcare",
  "jsonrpc": "2.0"
}
'

{
  "result": "<string>",
  "id": "<string>",
  "jsonrpc": "<string>"
}