I was testing about ~4000 simultaneous change feeds, when I managed to crash rethinkdb.exe with the following info on screen:

Version: rethinkdb 2.3.6-windows (MSC 190024215)
error: Error in thread 3 in src\rdb_protocol\changefeed.cc at line 1164:
error: Guarantee failed: [inserted]
error: Backtrace:
error: Thu Aug 2 16:04:55 2018

   1: 0x00007FF69447372F [The specified module could not be found.]
   2: 0x00007FF694474277 [Attempt to access invalid address.]
   3: 0x00007FF69485A151 [Attempt to access invalid address.]
   4: 0x00007FF69491C187 [Attempt to access invalid address.]
   5: 0x00007FF6948BC19E [Attempt to access invalid address.]
   6: 0x00007FF69492A367 [Attempt to access invalid address.]
   7: 0x00007FF6948CC2AE [Attempt to access invalid address.]
   8: 0x00007FF6948CC763 [Attempt to access invalid address.]
   9: 0x00007FF69446CC5E [Attempt to access invalid address.]
   10: 0x00007FF69446AFB5 [Attempt to access invalid address.]
   11: GetOsSafeBootMode+241

error: Exiting.

And the following info in the log:

2018-08-02T16:04:55.778041200 4534.512346s error: Error in thread 3 in src\rdb_protocol\changefeed.cc at line 1164:
2018-08-02T16:04:55.779039800 4534.514055s error: Guarantee failed: [inserted]
2018-08-02T16:04:55.780041100 4534.514719s error: Backtrace:
2018-08-02T16:04:55.800039700 4534.535016s error: Thu Aug 2 16:04:55 2018\n\n1: 0x00007FF69447372F [The specified module could not be found.]\n2: 0x00007FF694474277 [Attempt to access invalid address.]\n3: 0x00007FF69485A151 [Attempt to access invalid address.]\n4: 0x00007FF69491C187 [Attempt to access invalid address.]\n5: 0x00007FF6948BC19E [Attempt to access invalid address.]\n6: 0x00007FF69492A367 [Attempt to access invalid address.]\n7: 0x00007FF6948CC2AE [Attempt to access invalid address.]\n8: 0x00007FF6948CC763 [Attempt to access invalid address.]\n9: 0x00007FF69446CC5E [Attempt to access invalid address.]\n10: 0x00007FF69446AFB5 [Attempt to access invalid address.]\n11: GetOsSafeBootMode+241
2018-08-02T16:04:55.801039800 4534.536059s error: Exiting.

I'm not sure it's repeatable. I'll update if it is.

Thanks.