SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6ebf219017e78868eb6a59cca6ecb38f178e6886d2039e194675431344bc3d28' 
  AND token = '13if6OVVdcqY1VTKbvc8TjT8psuITvDhJcVmbC56nlI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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