[VladRussian2]

i'd speculate that Google is brought in because it is good PR, and Oracle, well, it sounds like healthcare.gov backend is running something like 4-6 node RAC (most probably Exadata). Good luck to them as they would really need it :)

[nostrademons]

Google SREs have a lot of experience managing very complex systems with very little downtime. There're certain architectural patterns and practices you can use if you want to keep a large distributed website highly-available.

Oracle I'd imagine is there for expertise with specific technologies.

Also, it's worth remembering that these are specific engineers who volunteered, and not their employers. So a lot is really who was willing to do it.