SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '40d996b173db13437a8c10209843a9d053e42df9c4604bbb14cefbaa67d8329d' 
  AND token = 'jQ0R0nfmUNSYMIhvQI+AwEwhPzcP7DtnmUxztMfzGCM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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