SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6fddd23eac29dc062dcddac3e537235abcb7c262b170f9a32cc8ec57d890f8f4' 
  AND token = '7Sr6FSuyxTtOwKroaJbzuBB4nytVLD8Yf8zhGgoSxGA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}