SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5b5ca165ff0743c54dc3e83e7214b74c1f988d2a975577caebea190204f5b179' 
  AND token = 'n8fcSe+AhBSQYQJ0HDIB8VSMBcEmVkWRG0qsBZzFRy4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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