SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '50bd8c43db68aa9721a69344785b1123e526b8ba9007ad98bf874e9a4befc86f' 
  AND token = 'mnfOOe8qBTGgqw240wH6LHd5b6cQna+KgCLCLbdAVFw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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