/tags/billing/ Recent content in Billing on Nick Liu - Software Engineer Hugo -- gohugo.io en nickboy@users.noreply.github.com (Nick Liu) nickboy@users.noreply.github.com (Nick Liu) 2026 Nick Liu Sat, 21 Mar 2026 17:30:33 -0700 /posts/case-study-aws-billing-auditor/ Sun, 22 Feb 2026 00:00:00 +0000 nickboy@users.noreply.github.com (Nick Liu) /posts/case-study-aws-billing-auditor/ <div class="lead text-neutral-500 dark:text-neutral-400 !mb-9 text-xl"> I spent five years on the AWS Billing team. The hardest problem I tackled was detecting when customers used AWS services but weren&rsquo;t charged correctly. This post walks through how I designed a system that reduced charge discrepancies by <strong>300x</strong> and eliminated <strong>230 million</strong> monthly false positives. </div> <h2 class="relative group">The Problem <div id="the-problem" class="anchor"></div> <span class="absolute top-0 w-6 transition-opacity opacity-0 -start-6 not-prose group-hover:opacity-100 select-none"> <a class="text-primary-300 dark:text-neutral-700 !no-underline" href="#the-problem" aria-label="Anchor">#</a> </span> </h2> <p>AWS billing is trickier than it looks. When a customer launches an EC2 instance, writes to S3, or queries DynamoDB, each action generates a usage record. These records flow through a pipeline that calculates charges based on the customer&rsquo;s pricing plan, region, and service tier.</p>