The reason? They treated the interview as a technical test instead of an operational simulation.

I’ve spent the last few years deconstructing these failure modes. Below is the internal rubric interviewers are implicitly scoring against.

THE NALSD "PHYSICS" TRAP

Most candidates think NALSD is just system design with stricter constraints. Internally, it is about physical limits and supply-chain reasoning.

In a standard design round, drawing a “Distributed Storage Service” box is acceptable. In NALSD, that box is a liability.

What interviewers look for:

Resource caps: If the problem requires 99.99% availability but you are given 500 HDDs with a 2% annualized failure rate, writing “erasure coding” is not a solution. Doing the math to prove the target is impossible is the correct signal.

The Bandwidth Wall: If you propose replicating 5PB of data across regions without calculating transfer time, you fail. Replicating 5PB over a 10Gbps link takes over a month.

Signal: Google hires custodians who count watts, rack units, and fiber capacity.

THE TROUBLESHOOTING "HERO" ANTI-PATTERN

Candidates often believe the goal is to find the root cause as fast as possible. Internally, finding the root cause too quickly is often a negative signal (guessing).

Many jump straight to grep error. This mirrors developer debugging, not SRE incident management.

The Rubric Rewards:

Mitigation > Resolution: Spending 20 minutes identifying a bug while traffic is broken is dangerous.

The one-change rule: Restarting a server AND clearing the cache simultaneously destroys observability. Automatic red flag.

Signal: Can you stop the bleeding without understanding why it’s bleeding yet?

THE "BLACK BOX" OBSERVABILITY FILTER

Post-2024, "metrics" are lagging indicators. We test for Kernel Intuition. Modern failures live between the metrics (e.g., a CPU reporting 50% usage but stalling on I/O wait).

The Rubric Rewards:

Syscall Fluency: Can you explain how to verify a process is stuck via strace or /proc inspection?

Ghost failures: When logs are clean, do you freeze? Or do you look for resource contention (file descriptors, inodes, ephemeral ports)?

Strong answer: "I’ll look for processes in D-state (Uninterruptible Sleep) to rule out disk contention," not "I'll check CPU."

THE FALSE CERTAINTY PENALTY

Confidence without data is a liability. Google SRE culture is built on epistemic humility.

The Rubric Rewards:

Hypothesis invalidation: Do you try to prove yourself right or wrong? SREs try to disprove their assumptions.

The "I Don't Know" Bonus: Saying "I don’t recall the command, but I need to inspect TCP window behavior" is valid. Bluffing is a fail.

THE CODING ROUND IS SCRIPTING JUDGMENT

It is not LeetCode. It is text processing under constraints.

We care about:

Input validation: Do you crash on empty lines?

Memory usage: Did you load a 100GB log file into RAM?

Readability: Can an on-call engineer understand this script at 3am?

Verbose, defensive code scores higher than clever one-liners.

A NOTE ON PREPARATION

Most prep material focuses on "Knowledge Acquisition." The Google SRE loop tests "Execution Sequencing"—doing the right known things in the right order under uncertainty.

I built a structured open-source handbook to specifically train this "Sequencing" muscle. It includes the NALS flowcharts and Linux command cheat sheets referenced above: https://github.com/AceInterviews/google-sre-interview-handbook

Discussion question: Have you noticed the shift toward partial-information troubleshooting scenarios in recent Google SRE loops?