Is there a 'better' database to use than Informix? What does Google use, for example? SQL by MS? And is it practical to switch? Though I have heard of Informix for quite some time, I just Googled it and found that it is an IBM product. I guess I am old, but I thought that IBM had a reputation for doing big iron, and a solid DB? Or has that ossified over the years?

*edit* Just took a closer look at the quick blurb on Google, and this caught my eye: Stable release: 12.10.xC7 / June 15, 2016. I can appreciate having something just work if it ain't broke, but I don't know, it seems to me that over 18 months between stable releases seems like a pretty long time in the compressed IT world we live in now. But then again, what do I know? ;-)

It is the BOINC master database which uses mySQL rather than the science databases that use Informix. The issue is more how SETI@home uses the database.
For all of the tasks assigned to hosts, "results out in the field", the task information is stored in a single table.
So when tasks are assigned, reported, or a host doesn't an update then that table is accessed.
For the hardware running the db the limit of that table turns out to be around 11,000,000 rows. Then it can not longer complete a query fast enough. Which causes the db server to stop and the project to be offline for several hours if not days which recovery is run.

So the solutions are
1) Have more hefty master and replica db servers.
2) Recode how the results are sent to hosts are stored.
3) Limit the number of tasks sent to hosts.

#1 is a stop gap until that hardware hits its limit.
#2 is probably the best solution, but requires dedicated time that isn't available to the project.
#3 easiest to implement and can be adjusted if the db server gets near the limit again.

#3 is the opposite of the thread title. One other thing that can be done is to shorten the amount of time until a report is due. The should shorten the queue of workunits out in the bushes and also let more workunits validate faster. However as Seti allows phones to crunch, I'm not sure how much shorter it can be before many of those low crunch able phones would start missing deadlines. Perhaps some sort of dynamic deadline based on the reported FLOPS?

As I just learned there is a maximum of 100 WUs per compute device, or device class, and with an average of about 4-5 minutes per WU, that's a maximum of about 8 hours of work I can store, and with the splitters out all the time recently, this really doesn't cut it.

I'm already out of work for two hours with the current outage.

A cache of 100 tasks is only about an 8 hour cache for my dual E5-2670, or R9 390X as well. When we have shorties it is even less.
There are a few options to handle running out of work during an outage.
1) Have a backup project in BOINC.
2) Let your system(s) have a break when they run out of work.
3) Not run the project.