Practice · SRE Principles, SLOs & Toil

Twenty-four single-best-answer questions covering the three modules the rest of the SREF blueprint quietly leans on: SRE Principles & Practices (Module 1), Service Level Objectives & Error Budgets (Module 2), and Reducing Toil (Module 3). This is a practice bank, not a mock — no 60-minute clock, no interleaving with the other five modules — so it drills these three until the vocabulary and the arithmetic stop needing deliberation: where SRE actually came from and how it differs precisely from DevOps, the SLI/SLO/SLA chain plus the formula that turns an SLO into a spendable number of minutes, and the six-property test that decides whether a recurring task legally counts as toil. Answer cold, in the exam's own four-option, single-best-answer format — every question explains not just which option is correct but which specific trap each wrong option was built from. This is the first of three module-grouped banks; Monitoring & SRE Tools and Anti-Fragility & Organizational Impact cover the remaining five modules.

What this bank drills, and how it's built

☺ Like you're 10: Same four-option, one-right-answer format as the real test — just three topics at a time instead of all eight mixed together.

The SRE Foundation (SREF) is a closed-book, 40-question, 60-minute, single-best-answer multiple-choice exam with a 65% pass mark, drawn from eight blueprint modules DevOps Institute doesn't publish a per-module weighting for. Every question below is written in that exact register — four options, exactly one correct, no partial credit for a well-reasoned wrong answer — because the format itself is part of what you're rehearsing, not just the content. Click an option to lock it in: it turns green or red immediately, and the explanation underneath names the specific reasoning, including which trap each wrong option was built from. The chips below the meta bar filter by module, the progress bar and counter track the current attempt, and Shuffle / reset reshuffles both the question order and each question's own option order, so passing a second time by remembering "the third one was green" doesn't work. Your attempt count and best score per module are kept in this browser only.

The three modules, and why they're grouped together

☺ Like you're 10: You can't reason about the budget without the frame from module one, and module three protects the engineering time module two's budget assumes you actually have.

The grouping isn't arbitrary — these are the three modules most people find genuinely sequential, in a way the exam's other five modules mostly aren't. Module 1 establishes what SRE is and how it precisely differs from DevOps and traditional operations, which is the frame every later module quietly assumes. Module 2 turns that frame into an actual number: an SLO target, and the error budget it produces once you subtract that target from 100% and multiply by a window. Module 3 is the operational discipline that number exists to protect — toil is exactly the kind of recurring, budget-draining, engineer-hour-consuming work that a healthy error-budget policy is trying to keep in check, which is why "reduce toil" and "spend the budget deliberately, not by accident" are two ends of the same idea.

How to work this bank

☺ Like you're 10: Go in cold, read every explanation even when you got it right, and write down what kind of mistake it was — not just which letter you should've picked.

Reading a practice bank once and nodding along teaches you almost nothing — the format only pays off if you use it the way it's meant to be used.

1. Go in cold. Close Know It Cold — SREF and the blueprint pages before you start a chip. If you've got a reference tab open while you answer, you're rehearsing search, not recall — a skill the real closed-book sitting gives you zero opportunity to use.
2. Commit to an answer before reading the explanation, even when you're guessing. A guess you got right for the wrong reason is worth catching now, while it's free.
3. Read every explanation, including the ones you got right. Half the value here is the sentence naming why the tempting wrong option looked correct — that sentence is the actual skill a single-best-answer exam is testing.
4. Log the module of every miss, not the question. Three chips, three possible diagnoses. Two misses in "Reducing Toil" and none elsewhere is a specific reading assignment; one miss scattered across each chip is closer to noise.
5. Re-sit the weak chip a day later, without re-reading the explanations first. Getting it right the second time for the same reason as the first time is genuinely learned; getting it right because you remember which letter was green last time hasn't taught you anything.

The bank — 24 questions

☺ Like you're 10: Pick an answer. It turns green or red immediately and tells you exactly why.

Eight questions per module, in the exam's own four-option, single-best-answer shape. The chips filter by module; "All 24" runs the full set interleaved, which is closer to what a real sitting actually feels like once you've drilled each module on its own first.

The error-budget arithmetic, worked longhand

☺ Like you're 10: One formula and one table of minutes-per-window — memorize both and almost any error-budget question turns into simple multiplication.

Module 2's arithmetic only requires two things held cold: the formula, and how many minutes live inside whatever window a question hands you. This is the exact same table used on Know It Cold — SREF — reproduced here longhand, Sol-style, because a bank drilling this arithmetic should show its work rather than assume it.

Error budget = (100% − SLO) × window, in the window's own units

Step 1 — convert the window to minutes (30-day month = 43,200 min, unless told otherwise)
Step 2 — subtract the SLO from 100% to get the allowed failure rate
Step 3 — multiply the failure rate by the window

Notice the pattern that makes this table reconstructible on exam day even if one cell blanks out: each additional nine divides the allowed downtime by roughly 10x. Hold 99.9% → 43.2 minutes a month cold, and you can derive 99.99% by dividing by ten and 99% by multiplying by ten, without having memorized every row as an isolated fact.

To drill this arithmetic against a timer rather than reading it, run Drill — SLO & Error-Budget Calculation, and see the policy actually bite in Google & the error-budget policy.

Distinctions this bank keeps returning to

☺ Like you're 10: Here are the lookalike pairs the questions above kept testing, side by side, so the difference stops needing to be re-derived every time.

If you can produce the right-hand column from memory without looking, these three modules are close to done.

If you missed these, read this

☺ Like you're 10: Find the chip you dropped marks in, read the page next to it, then go re-sit that chip alone.

Nothing tested above is examined anywhere on this site without also being taught somewhere on this site. Take a miss one module at a time — the middle column is the exam-blueprint version of the idea, the right column is where it's taught at full depth.

Where to go next

☺ Like you're 10: Three foundational modules are done — two more grouped banks and a full timed mock stand between here and the real exam.

Modules 1–3 are one third of the blueprint. Work the other two grouped banks the same way — cold, chip by chip, explanations read even when you were right — and only then sit a full mock, since a mock is a measurement and measurements are wasted on material you haven't drilled yet.