There is a limit For optimal performance, there are default limits of 50 business transactions per app agent and 200 business transactions per business application. There is no limit at the tier level.
The app agent limit of 50 business transactions applies to each app agent, not to the machine. If you have multiple app agents on a single machine, the machine can handle the number of agents times 50.
If traffic exceeds the 50 business transaction per app agent limit or the 200 business transaction per application limitdefault limits, the traffic from what would be 51st detected business transaction and greater for the agent or the 201st and greater detected business transaction for the application is collected into a default business transaction called "All Other Traffic - <tier_name>". There is one of these "All Other Traffic" default transactions for each tier. There is no limit at the tier level.
Some applications, such as those that create business transactions dynamically, can exceed the default limits very quickly. Since you want to monitor the business transactions that are key to your business, look at All Other Traffic and decide whether any of it needs to be reconfigured. See Managing All Other Traffic and Configure Business Transaction Detection.