OIC - There are large number of scheduled orchestrated integrations need to run at the same time. What we can do to avoid backlogged or queued integrations ?

When there are too many scheduled integrations configured, instances can get backlogged waiting for resources to become available or previous integration runs to complete. This can cause processing delays where some instances are in a waiting state longer than they should be and schedules may not start at the scheduled time.

If we absolutely require a large number of scheduled integrations,  recommend the following design changes as a solution:

1. For each scheduled integration, convert it to an application-driven orchestrated, REST Adapter trigger-based integration. 
2. Create a new scheduled integration that only performs an asynchronous invoke of the application-driven orchestrated integration you converted in step 1 above.

Benefits of the design:

This solution enables the scheduled integration to start at the scheduled time, invoke the REST Adapter trigger-based child integration asynchronously, and complete within milliseconds. This approach reduces the backlog and contention surrounding scheduler resources.

If you have a large number of scheduled integrations to convert, a staged approach starting with the following integrations is recommended.

1. Longest-running scheduled integrations.
2. Scheduled integrations configured with the shortest frequency (for example, integrations that run every 10 minutes or less).

In the above screenshot,  I have created one schedule integration which is calling app driven integration where i have intentionally put 5 mins of wait. When I run the schedule one, it completes in mili second , where as app driven is still running.

Reference:

https://docs.oracle.com/en/cloud/paas/integration-cloud/integrations-user/common-integration-style-pitfalls-and-design-best-practices.html