Please take another look; we introduced custom machine types back in November:<p><pre><code>  http:&#x2F;&#x2F;googlecloudplatform.blogspot.com&#x2F;2015&#x2F;11&#x2F;introducing-Custom-Machine-Types-the-freedom-to-configure-the-best-VM-shape-for-your-workload.html
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Which would let you adjust your RAM to vCPU ratio (as low as ~1 GiB per vCPU and up to 6.5).<p>Disclaimer: I work on Compute Engine.