How to store and refresh cache in CPO 2.3?

Question

                   We have some dozen workflows (CPO 2.3 processes) each triggered to start by a unique tidal event. Each workflow when triggered fetches numeric data (just two or three two-digit data such as 15, 300) from a singluar web service  end point and uses the same in its workflow logic. Data fetched by each workflow is usually specific to that workflow. We want the workflow to cache locally the data thus fetched. Reason for caching data locally in CPO: The rate of web service lookups is 100+ lookups per second and the web service cannot scale beyond 100 lookups per second. The data thus cached will be local to that workflow.
QUESTIONS PLEASE:
1. What is the best way to store the fetched data? Is it using local variables or global variables or some other storage mechanism?
2. Should the data thus cached be fetched each time the process (workflow) is re-started?
3. When the data is changed at the web service, the web service can send fresh data back to CPO to refresh the previously cached data. What is the best way to receive this data in order to refresh the local cache in CPO while the worklfow is running and operational [(i.e) without disrupting the workflow's running state]?
Will appreciate detailed answers please to avoid follow up questions.
thanks in advance,
Jamal

Answer 1

Thanks to Von and Mike for responding. I have summarized your responses to my specific questions. Please see if my summary/understanding of your responses is right.
QUESTIONS:
1) Can the PO process create a global table variable containing say 20,000 entries? If not, what's the max limit?
RESPONSE: There is no max limit to the number of rows in a table variable (global or local).
2) Assuming the PO process can build a global table variable containing 20,000 entries, will a lookup for ThresholdData given a DeviceIPAddress be VERY SLOW making the PO process inefficient?
RESPONSE: select statement to query a table it's pretty fast.  If you looped trying to find a match, it would be incredibly slow.
- Let's say at time Tn, the number of entries in the global table variable is 20,000.
- Let's say at time Tn+1, the ThresholdData for 8000 (of the 20,000) devices got changed in the web service DB.
QUESTIONS:
3) Can the web service send ThresholdData for 8000 devices using a table variable of type INPUT? I did not see a table variable for type INPUT supported by a PO process and hence this question.
RESPONSE: wrap table data in CDATA tags in XML, then read it into a table once it gets into the process.
Now to answer some of your questions:
1. We are planning on using CPO 2.3 to act as a Real time Alert Notification tool to send email notifications to our NoC Operations personnel. We would like to send a notification within 3-5 mins of TCA generation (yes - TCAs come from a performance management tool such as InfoVista).
2. Tidal's workflow is expected to do some validation on a received TCA, before deciding to send a email notification. For example, Tidal will wait for 15 minutes upon receiving a MAJOR/CRITICAL TCA to see if a CLEAR arrives for that TCA within that 15 minutes interval. If so, Tidal  workflow will generate a mail notification, if not, it will do nothing. Like this, we have many HIGHER LEVEL VALIDATION RULES that CANNOT BE PERFORMED AT PERFORMANCE MGR LEVEL. They can only be performed at the level of tidal that supports easy to write rules GUI and easy to change the rules in a matter of minutes.
3. No - we do not have 50,000 processes. We will have utmost 25 processes (workflows) - one for each TCA type coming out of InfoVista. Each process will know how to treat a TCA type before generating an email notification.
4. The number 50,000 corresponds to Devices in our Network. The validation rules that will be implemented in tidal workflow shall use data such as the 15 minutes mentioned above. An external DB shall maintain the list of 50K devices and the 'time-to-wait-for-CLEAR' data for each of the 50 K devices. Like 'time-to-wait-for-CLEAR' data, we have other data for other validation rules that will be implemented using tidal workflow for the various TCAs that we intend to support. This DB shall be exposed to Tidal workflow via a Web Services API.
Hope our use case is now clear. If so, please do add your 2c that will help answer my original questions. I can also go on a call to explain our use case. If you think I should engage with your services team, please send me their contact details and I will do so.
Thanks for all the support.