We made the Tune, but only after Purge, as  Vitaliy suggested, it works fine.

Thanks a lot.

Thanks! 
But:
1) it doesn't help
2) I don't want to guess, I want to know, how and why.

Thanks again :)

Class Portal.ProductStats Extends %Persistent
{

Property Item As %String [ Required ];

Property dateImported As %String [ Required ];

Index pcacheUpds On Item;
}
Class Portal.ProductCacheUpdates Extends %Persistent
{

Property Product As %String [ Required ];

Property Item As %String [ Calculated, SqlComputeCode = { s {*}=$e({Product},1,5)}, SqlComputed ];

Property dateEdited As %String [ Required ];

Index pcacheUpdsUniq On (Product, Item) [ Unique ];

Index pcacheUpdsProd On Item;

}

Cache for Windows (x86-64) 2017.2 (Build 744U) Fri Sep 29 2017 10:58:27 EDT

Thanks Alex,
You are right, the api/atelier/ application was disabled.