Unfortunately, due to the way that After Effects is invoked from the CLI when a batch is run, Templater will always spin up an AE instance, render the data that’s been passed over, and then close out. There isn’t a way to force Templater to stay open and await further data without using Templater Bot.
I’m assuming that using Bot isn’t an option due to the real-time processing requirement of this project. If that’s the case, and the time that Templater takes to spin up, process, close, and re-open is introducing a delay into the system, the only recommendation that I could make would be to run multiple instances of Templater Bot simultaneously so that new entries in the data source could be passed off to a fresh system while the previous one closes out the last job batch.
If those assumptions are incorrect, or if there are some details that I’m missing, please feel free to let us know any additional information about the project that might help us to make a better suggestion.