Security Considerations To Account for When Redirecting From Microservice to Another

The biggest possible security implication I can see with the details presented is that you might accidentally DoS your visitors if every individual service has its own session, and therefore session cookie. Once you hit the cookie limit (typically 4096 bytes), browsers will start ignoring cookies, possibly arbitrary ones, and that will cause sessions to start being dropped.

Another possible vulnerability is that if you have to examine multiple sessions in order to do work, it's possible that a malicious user might send a large number of different session ids, real or otherwise, and force your services to examine each one, which at best would cost CPU cycles (and thus money), and at worst cause a wider system DoS.

Both of these would be mitigated by only having a single session for the user.