Why does JustOn feel "slow"?
As you know, JustOn Billing & Invoice Management runs as an integrated application on Salesforce Platform, the cloud-based platform for software development and operation from Salesforce. When operating JustOn, you may sometimes experience performance drops. This is usually not the result of a failure, but a "collateral cost" of cloud computing.
On cloud-based platforms, you use computer system resources, especially data storage and computing power, shared via the Internet. Generally, this allows enterprises to focus on their competence, without the need to care for IT and infrastructure. However, the cloud vendor distributes the shared resources to all cloud users, allocating a certain "portion" of them to each user for a given period.
Your Salesforce org is hosted on one of Salesforce's computing instances, together with many other customers and their orgs. That is, you share the instance's resources with all of them. Now depending on the number of customers and orgs on that instance as well as the number of users currently working, you may temporarily experience performance decreases.
Generally, Salesforce enforces limits so that certain code or processes do not monopolize shared resources. However, it allocates more computing resources to batch processes (asynchronous transactions) than to other code (synchronous transactions): more SOQL queries, more CPU time, more memory (see Execution Governors and Limits in the Salesforce Help). Consequently, using batch processes allows for handling more data and executing more calculations in one operation.
JustOn therefore recommends to automate and schedule large bulk operations, like invoice runs, exports or email distributions, to be executed at night or on weekends. This is a simple way to distribute the load your that org produces: resource-consuming processes run when no (or only a few) users are online, and your users can do their work without being slowed down by bulk jobs.