Just added the custom-db-appender quick start, and what I found was that if command logging is used, we should also recommend using the async-handler:

<async-handler name="ASYNC">
<level name="DEBUG"/>
<queue-length value="1024"/>
<overflow-action value="block"/>
<subhandlers>
<handler name="COMMAND"/>
</subhandlers>
</async-handler>

Otherwise, Teiid is blocked until the write is completed. And I didn't see any information that needed (like any timing info) that required it be synchronously processed. Also, wasn't sure if this info would be better suited on the custom logging page or here.