EC2 |

Page-cache thrashing on EC2: kill the tenant before it takes the host down

Oct 28, 2026 · 30 min read · Linux EC2 container ·
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For a long time, some of our container hosts, most often the smallest ones, would go dark every so often. A t3.micro with 1 GiB of memory, running a customer's containers, would stop sending logs and metrics all at once and never start again. The orchestrator still showed every container as RUNNING. The only signs of …

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Detect and fix rare cases where the primary ENI does not serve default traffic

Jul 27, 2025 · 3 min read · Linux EC2 ·
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During testing, we encountered a rare scenario when launching EC2 instances with multiple ENIs: the primary ENI (device index 0) does not serve default network traffic. This occurs in approximately 1 out of 10,000 launches (0.01%). For example, when configuring two ENIs on an instance—ENI-0 (deviceIndex=0) from …

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