SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b68e38f1311d02be843cf365d6658b2a4632989c8b699b24eee78057f87c7ca7' 
  AND token = 'c0mXQqZjxjI9w9VSUq1eLkXryqDNujQVaDvk+KCjCuE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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