I've been using Openresty (with Lua and Redis support) to collect a large amount of data from GET requests for a video sharing site. Having nginx push data directly into Redis is super fast, lends easily to real-time metrics, and makes it easy to batch everything up and push it into MySQL at the end of the day. Now that Redis supports internal Lua scripts, you can also do custom atomic functions and other neat things.

If you can get around the Redis SPOF, OpenResty + Redis is great for large-volume data collection. Thousands of requests/sec on an EC2 Small at < 10% load.