Would you use MongoDB in high-transaction environment? using other words:

does the one-write-lock-per-database policy (it's not a "bug" but a "feature" by design) affect contention making its usage in certain kind of workloads less then optimal?

if not how do you maintain that kind of workload? 

would you use an async-write-queue  at the application level? (roll-backing would be difficult with such a structure though)
MongoDB can survive high concurrency writes, so long as you engineer for it.


INSERTs are about the same size.
Very little UPDATE going on.
Shard to add write concurrency scalability.


The things that will kill you on write scalability will be updates that go past the built in padding factor, as that triggers a double write as the block is relocated to a larger free spot. If your document sizes are within a narrow range and updates don't change the size much, it can scale quite far.