The problem is we have multiple systems (each system is made up of several microservices) and there are many different entities flowing through these systems.
We need a way to monitor specific flows/transactions so we can see the entire flow of an entity between all the systems in order to detect problems.

What we have now is each system sends events to our service, and we correlate these events based on different criteria from the events to display a full trace, however we found this to be not very scalable and are looking for better ways to achieve this.

how should we go about implementing this? what technologies/system architectures should we look into?

any help is appreciated,
thank you