Current database index nflow_workflow_activation is unoptimal for polling.

[jsyrjala]

Currently nFlow has this index which is intended to make polling fast.

create index nflow_workflow_activation on nflow_workflow(next_activation, modified);

Now days this doesn't match any more the polling code:
https://github.com/NitorCreations/nflow/blob/master/nflow-engine/src/main/java/io/nflow/engine/internal/dao/WorkflowInstanceDao.java#L516

String whereConditionForInstanceUpdate() {
  return "where executor_id is null and status in (" + sqlVariants.workflowStatus(created) + ", "
      + sqlVariants.workflowStatus(inProgress) + ") and " + sqlVariants.dateLtEqDiff("next_activation", "current_timestamp")
      + " and " + executorInfo.getExecutorGroupCondition() + " order by next_activation asc";
}

There should be an index that is something like this to replace the current index

create index nflow_workflow_activation2 on nflow_workflow (next_activation, executor_id, status, executor_group);

[efonsell]

Fixed in PR #343