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

const options = {
  method: 'POST',
  headers: {'Content-Type': 'application/json'},
  body: JSON.stringify({
    method: 'broadcast_tx_async',
    params: {
      signed_tx_base64: 'aSDinaTvuI8gbWludGxpZnk=',
      wait_until: 'EXECUTED_OPTIMISTIC'
    },
    id: 'dontcare',
    jsonrpc: '2.0'
  })
};

fetch('https://api.example.com/broadcast_tx_async', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

import requests

url = "https://api.example.com/broadcast_tx_async"

payload = {
    "method": "broadcast_tx_async",
    "params": {
        "signed_tx_base64": "aSDinaTvuI8gbWludGxpZnk=",
        "wait_until": "EXECUTED_OPTIMISTIC"
    },
    "id": "dontcare",
    "jsonrpc": "2.0"
}
headers = {"Content-Type": "application/json"}

response = requests.post(url, json=payload, headers=headers)

print(response.text)

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