Projects on Nick Liu - Software Engineer

AWS Billing Unbilled Usage Auditor

nickboy@users.noreply.github.com (Nick Liu) — Mon, 01 Jan 0001 00:00:00 +0000

Designed and built a distributed system that detects unbilled usage across all AWS services — reducing charge discrepancies by 300x and eliminating 230 million monthly false positives.

Key Metrics
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300x Reduction in Discrepancies

$125,000 → $432

230M False Positives Eliminated

~95% Alert Actionability

Architecture
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flowchart LR
    A["Usage Records\n(Billions/day)"] --> B["Smart Sampling\n& Aggregation"]
    B --> C["Multi-Signal\nValidation"]
    C --> D["Automated\nResolution"]
    D --> E{Real issue?}
    E -- Yes --> F["Alert with\nDiagnosis"]
    E -- No --> G["Auto-resolve\n& Log"]
    style B fill:#6366f1,color:#fff
    style C fill:#6366f1,color:#fff
    style D fill:#6366f1,color:#fff

Technical Deep Dive
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Aggregation over Brute-Force
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Instead of checking every individual usage record (which generated 230M false positives), the system aggregates at the service-account-period level.

Twitter Fleet-Scale Kernel Automation

nickboy@users.noreply.github.com (Nick Liu) — Mon, 01 Jan 0001 00:00:00 +0000

Built the automation and validation tooling to manage kernel updates across 5,000+ production servers at Twitter — with zero-downtime progressive rollouts and automated canary validation.

Key Metrics
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5,000+ Production Hosts

Weeks → Days Rollout Time

140+ Tickets in One On-Call Week

Zero-Downtime Updates

Architecture
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flowchart LR
    A["New Kernel\nVersion"] --> B["Canary\nValidation"]
    B --> C["Wave 1\n1% Fleet"]
    C --> D["Wave 2\n5% Fleet"]
    D --> E["Wave 3\n25% Fleet"]
    E --> F["Full Fleet\nRollout"]
    C -- anomaly --> G["Pause &\nAuto-Alert"]
    D -- anomaly --> G
    E -- anomaly --> G
    style B fill:#6366f1,color:#fff
    style C fill:#6366f1,color:#fff
    style D fill:#6366f1,color:#fff
    style E fill:#6366f1,color:#fff
    style F fill:#6366f1,color:#fff

Technical Deep Dive
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Validate Before You Roll
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A Python library that validates kernel safety before fleet-wide rollout:

Projects on Nick Liu - Software Engineer

AWS Billing Unbilled Usage Auditor

Key Metrics #

Architecture #

Technical Deep Dive #

Aggregation over Brute-Force #

Twitter Fleet-Scale Kernel Automation

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Architecture #

Technical Deep Dive #

Validate Before You Roll #

Key Metrics
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Architecture
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Technical Deep Dive
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Aggregation over Brute-Force
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Key Metrics
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Architecture
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Technical Deep Dive
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Validate Before You Roll
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