Hi @turquoiseowl ,
I'm using i18n for the last 2 years in my web app and now we're working on the performance improvement.
While profiling my application, we found that the i18n module takes more CPU time compared to other modules. So we've removed i18n from the web app and load tested the app. We got the below results,

25 users with 5 minutes duration
With i18n,
Avg Response time: 348.7 ms
Request pre sec: 44.7RPS
CPU usage: 95%

Without i18n,
Avg Response time: 161.5 ms
Request pre sec: 70.2RPS
CPU usage: 50%

We're using the below keys in the web.config:

<add key="i18n.DirectoriesToScan" value=".." />
 <!-- Rel to web.config file -->
 <add key="i18n.WhiteList" value="*.cs;*.cshtml;*.sitemap;*.js" />
 <add key="i18n.BlackList" value=".\SampleReports;.\Scripts\AngularJS;.\Scripts\Bootstrap;.\Scripts\EssentialJS;.\Scripts\Jcrop;.\Scripts\jQuery;" />
 <add key="i18n.NuggetBeginToken" value="[[[" />
 <add key="i18n.NuggetEndToken" value="]]]" />
 <add key="i18n.NuggetDelimiterToken" value="||||" />
 <add key="i18n.NuggetCommentToken" value="////" />
 <add key="i18n.NuggetParameterBeginToken" value="(((" />
 <add key="i18n.NuggetParameterEndToken" value=")))" />

Are these results are normal or do you have any suggestion to improve the performance?