I think a better strategy is to store logs in flat files with several replicas. Do your metric generation in realtime, regexing a bunch of logs on a bunch of workers as they come in. (I handled > 250MB/s on less than one Google production machine, though did eventually shard it up for better schedulability and disaster resilience. Also those 10Gb NICs start to feel slow when a bunch of log sources come back after a power outage!)
For simple lookups like "show me all the logs in the last 5 minutes", you can maintain an index of timestamp -> log file in a standard database, and do additional filtering on whatever is retrieving the files. You can also probably afford to index other things, like x-request-id and maybe a trigram index of messages, and actually be able to debug full request cycles in a handful of milliseconds when necessary. For complicated queries, you can just mapreduce it. After using ES, you will also be impressed at how fast grepping a flat file for your search term is.
The problem is, the machinery to do this easily doesn't exist. Everything is designed for average performance at large scale, instead of great performance at medium scale. Someday I plan to fix this, but I just don't see a business case, so it's low priority. Would you fund someone who can make your log queries faster? Nope. "Next time we won't have a production issue that the logs will help debug." And so, there's nothing good.