I think it's still a bug: imagine two tenants with separate schemas (s1 and s2) and two appserver (a1 and a2) and increment-size = 10 follwoing sequence:

1st request (s1, a1): the optimizer gets id = 0 - sequence table in s1 will be updated
2nd request (s2, a1): the optimizer gets id = 1
3rd request (s2, a2): the optimizer gets id = 0 - still no constraint violation, sequence table in s2 will be updated
4th request (s2, a2): the optimizer gets id = 1 - now you get a constraint violation

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