# FAQs
These are known and common FAQs. We welcome you to contribute yours.

## Design
* [Why doesn't SkyWalking involve MQ in the architecture?](why_mq_not_involved.md)

## Compiling
* [Protoc plugin fails in maven build](Protoc-Plugin-Fails-When-Build.md)
* [Required items could not be found, when import project into Eclipse](Import-Project-Eclipse-RequireItems-Exception.md)

## Runtime
* [Why only traces in UI?](Why-have-traces-no-others.md)
* [Too many GRPC logs in the console](Too-many-gRPC-logs.md)
* [The trace doesn't continue in kafka consumer side](kafka-plugin.md)
* [Agent or collector version upgrade](Upgrade.md)
* [EnhanceRequireObjectCache class cast exception](EnhanceRequireObjectCache-Cast-Exception.md)
* [ElasticSearch server performance FAQ, including ERROR CODE:429](ES-Server-FAQ.md)
* [IllegalStateException when install Java agent on WebSphere 7](install_agent_on_websphere.md)
* ["FORBIDDEN/12/index read-only / allow delete (api)" appears in the log](https://discuss.elastic.co/t/forbidden-12-index-read-only-allow-delete-api/110282)
* [No data shown and backend replies with "Variable 'serviceId' has coerced Null value for NonNull type 'ID!'"](time-and-timezone.md)
* [**Unexpected endpoint register** warning after 6.6.0](Unexpected-endpoint-register.md)