Day 34 drills

Answer from memory after reading the papers. Comprehension, not trivia.

D1 (Dynamo: two mechanisms to stay writable when nodes are down, and the mess + cleanup):

D2 (Dynamo: what R, W, N mean, and why an always-writable store might set W low):

D3 (Bigtable: SSTables as an LSM engine, what it buys over a B-tree at that write volume):

D4 (Spanner: why TrueTime returns an interval, and why it has to wait):

D5 (one line each: what Dynamo, Bigtable, Spanner each gave up and bought):