That’s not easy because the condition is dynamic and only known by the data managers (invariant wasn’t an appropriate name). Certainly much harder than an offline generation.
My proposal is the following:
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client asks for ID1
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vault managing ID1 stores the corresponding ID2 and ask for it
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vault managing ID2 returns the data (possibly directly to client)
The second vault gets the reward on ID2 but doesn’t know that he has to issue a get on ID1 to fetch the data.
The 2 vaults should be far enough so that in case of merge the 2 ids don’t risk to be stored in the same vault.