SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ad1ec4fa083db5a6efce950a9cfb0f20575ee1dc9844994dccc8765779822e6f' 
  AND token = 'bMXMaWQy2NpXKHXFpvAZKtyhRbi+zr4JOLRd7MxtH0U=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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