Need suggestions for tool in production to run many API calls, polling every few minutes

Has anyone used Zapier or alternative API integration tools? It gives something like 17500 calls per month on the price plan we are on. We are going to run out. We’d like to use another (cheaper) alternative tool.

The requirement:
To be able to sequence API calls
To be able to configure how often the system checks for changes, and fires the chain of API events as required.
The chain of calls must be configurable.
The tool should be codeless, i.e. a GUI. The users are technical but not coders.
Events should be able to run in parallel, i.e. if 2 conditions are met, then 2 chains of events should be able to run, so they don’t block the other one from running, if conditions for 2 or more chains are true.

Context:
We have multiple systems that talk to each other with APIs when events happen. Zapier listens on the tools and fires events so the other systems do their respective actions. E.g. when a user sets up X event in tool A, it sends messages to Slack and adds reminders to calendars. Zapier polls for changes every few minutes or so (it is configurable how long the intervals are).

When setting up a new user in Gsuite, it messages Slack and adds them as a user to various systems as a new user.

Events can fire many APIs, so each event uses up a lot of the quota.

Wondering where there can be efficiencies in the number of calls in the long term but in the meantime, need more capacity on Zapier/alternative system at lower cost.

Possible (inadequate) solutions
Could probably be done with Postman but that won’t be running anywhere, is manual to kick it off, and won’t be polling for events. So that would work for individual events but not for a massive suite of actions.

There is no CI pipeline. Suggestions welcome.

Thanks
Mike

Out of curiosity, would you be prevented from creating a CI pipeline just for Postman? Jenkins is super easy to setup, and you can then have your Postman stuff triggered as regularly as you like.

I think it would be more a technical barrier as we are a charity with only me (not that technical) and 1 other ( a dev with a day job). Neither of us are experts in APIs. The API stuff is currently in Zapier, which is adequate but running oit of capacity on the current plan. It is a GUI.

If we move to Postman etc it would need to be coded, and that’s where I am not experienced, and Js is not fun either, and neither my nor my colleague’s skillset.

We would be reinventing the wheel in stages if/when we transfer to whatever new system we choose, whether that is a GUI or Newman or whatever.

Anything Postman/Newman would require code.