Comparison
Reserved capacityvsSpot instance
Reserved capacity
you promise a year of spend in advance and pay perhaps forty percent less, and you owe it whether or not you use it.
Committing to a level of usage over one or three years in exchange for a substantial discount. It is close to free money for a stable baseline and a liability if the architecture changes underneath it — a migration that halves your compute leaves the commitment intact. The practical approach is to commit only to the floor you are confident of and leave the variable part on demand.
Full entry →Spot instance
the machine costs a fraction of the normal price and can be taken away from you with two minutes' notice.
Buying spare capacity at a steep discount on the condition that the provider may reclaim it. It is excellent for anything interruptible and replayable — batch, builds, stateless workers — and hostile to anything that cannot be moved quickly. Using it well means diversifying across instance types and zones so a reclamation in one pool does not take your whole fleet.
Full entry →