How does a hybrid EC2 and Lambda strategy maximise cloud efficiency?

Quick answer: run a baseline of EC2 for steady, predictable compute (cheaper per hour than Lambda at constant load) and use Lambda to absorb traffic spikes on top of it — the combination gives you a cheap floor and elastic ceiling instead of over-provisioning EC2 for peak load you rarely hit.

We can combine a couple of strategies to be really strong with our approach. We can have something running on an EC2 machine that gives us a baseline amount of CPU compute, and it's relatively cheap compared to Lambda. We can then tie that to Lambda to deal with our peaks when we're really busy, and by mixing the two together we get a blend of a cheap base cost and a slightly more expensive peaky cost, to work with our traffic flows if they're not really flat and predictable.