Invalidate cache issue

Hi everybody again. I've just created

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<PopulateCache async="false" continueOnError="false" enabled="true" name="OpenCache">
    <DisplayName>OpenCache</DisplayName>
    <Properties/>
    <CacheKey>
        <KeyFragment ref="MessageID"/>
    </CacheKey>
    <CacheResource>SessionCache</CacheResource>
    <Scope>Global</Scope>
    <ExpirySettings>
        <TimeoutInSec>3600</TimeoutInSec>
    </ExpirySettings>
    <Source>uuid</Source>
</PopulateCache> 

and then build the simple chain LookupCache --> InvalidateCache --> LookupCache. the issue is that invalidate cache doesn't work. My second LookupCache still see the value stored in cache

My Invalidate Cache

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<InvalidateCache async="false" continueOnError="false" enabled="true" name="InvalidateSession">
    <DisplayName>InvalidateSession</DisplayName>
    <Properties/>
    <CacheKey>
        <KeyFragment ref="UUIDfromCache"/>
    </CacheKey>
    <CacheResource>SessionCache</CacheResource>
    <Scope>Exclusive</Scope>
    <!--<CacheContext>-->
    <!--    <APIProxyName>CachedProxy</APIProxyName>-->
    <!--    <ProxyName>default</ProxyName>-->
    <!--    <TargetName>default</TargetName>-->
    <!--</CacheContext>-->
    <PurgeChildEntries>false</PurgeChildEntries>
</InvalidateCache>

And Lookup

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<LookupCache async="false" continueOnError="false" enabled="true" name="GetUUIDFromCache">
    <DisplayName>GetUUIDFromCache</DisplayName>
    <Properties/>
    <CacheKey>
        <KeyFragment>rrt333ea-2722-940940-1</KeyFragment>
    </CacheKey>
    <CacheResource>SessionCache</CacheResource>
    <Scope>Global</Scope>
    <AssignTo>UUIDfromCache</AssignTo>
</LookupCache>

And I have one more question. I use messageid as key. Is it a good idea?