curl --request POST \
  --url 'https://rpc-mainnet.solanatracker.io/?api_key=' \
  --header 'Content-Type: application/json' \
  --data '
{
  "jsonrpc": "2.0",
  "id": "db16f277-1a22-41ff-9f85-f37e2cd77900",
  "method": "getMaxRetransmitSlot"
}
'

{
  "jsonrpc": "2.0",
  "id": "db16f277-1a22-41ff-9f85-f37e2cd77900",
  "result": 1234
}