SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b646b704e032de9ecf198af430fd4686ae883ca4d8b15e4b202bb51e456f760d' 
  AND token = '0u/0g+aKDyNDrPZRAojPoTRdPc84HxVbFkyqzAchELE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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