Symptom: You're experiencing very slow performance from NuGet searches in Visual Studio or using the NuGet Package Explorer
Check the size of the sonatype-work/nexus/nuget/odata.h2.db file. If it is very large (as in over 1Gb) then you will likely see poor performance when searching for NuGet components. The typical cause for large size is having a "download nuget feed" task scheduled for your nuget.org proxy repository with "fetch all versions" enabled, over time this can cause the NuGet database to grow to where it causes performance problems.
To rebuild the database, shut down Nexus, remove or rename sonatype-work/nexus/nuget, and then restart. After starting, schedule "rebuild nuget feed" tasks to run against any hosted NuGet repositories you have.