Follow-up for T262391 and it's non-public counterpart T262240.
In T262391#6449590 et seq, @Bawolff proposed to limit concurrency of DPL queries by two ways: a query cache (which makes DPL to not do the same work XY times) and a pool counter that makes DPL to not work at more than X things at once.
Both should make DPL somehow safer (but not faster), which is always a bonus.