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Comprehensive and Detailed Explanation From Exact Extract:

Defense-in-Depth (DiD) is a layered security strategy referenced in SRE’s discussions of secure infrastructure and resilience. The perimeter layer is responsible for controlling and monitoring traffic flowing into and out of the network from external sources, such as the public Internet. This includes firewalls, intrusion detection systems, load balancers, and boundary network controls.

While SRE focuses primarily on reliability, the SRE Book stresses the importance of resilient system boundaries: “Perimeter protections are critical where external traffic enters the system.” (SRE Book – Security and Infrastructure considerations).

Option C correctly identifies the Perimeter Layer as the network boundary where data flows in/out from other networks—including the Internet.

Option A (Host layer) secures individual machines.

Option B (Physical layer) refers to hardware, power, racks, etc.

Option D (Data layer) protects stored data, not ingress/egress traffic.

Thus, C is correct.

Comprehensive and Detailed Explanation From Exact Extract:

A Service Level Indicator (SLI) is a measurement of some aspect of reliability (e.g., latency, availability, quality). One of its defining characteristics is that it must be measured over a specific time window. Without a time horizon, the SLI has no actionable meaning.

From the Site Reliability Engineering Book, Chapter “Service Level Indicators”:

“An SLI is a quantitative measure of some aspect of the level of service that is provided. SLIs are evaluated over a specific period of time in order to understand reliability as experienced by the user.”

The SRE Workbook further states:

“Every SLI must define a measurement window. Without a time horizon, the indicator cannot be used to calculate SLO compliance.”

Why the other options are incorrect:

A SLIs do not need to appear in an SLA; SLAs are external contracts, SLOs/SLIs are internal engineering tools.

B SLIs may include client-side, server-side, or network metrics depending on what reflects user experience.

D SLI agreement is not defined by SRE vs. Agile teams; it is defined by business and user need.

Thus, the correct answer is C.

Comprehensive and Detailed Explanation From Exact Extract:

Error budgets represent the allowable amount of unreliability in a system. Google defines the purpose of error budgets as: “balancing the pace of innovation with the need for reliability.” (SRE Book – Service Level Objectives). When the error budget is healthy, product teams can release features quickly; when it is exhausted, reliability work takes priority. This balance prevents over-investment in reliability and enables safe innovation.

Option B—innovation and reliability—is the exact phrasing used in Google’s SRE literature.

Options A, C, and D do not reflect the core purpose of error budgets.

Thus, B is the correct answer.

Comprehensive and Detailed Explanation From Exact Extract:

SRE-led service automation focuses on making environments reproducible, reliable, and consistent. One of the key principles aligned with Google SRE practices is the use of Infrastructure as Code (IaC), which allows environments to be provisioned automatically, consistently, and predictably.

The Site Reliability Engineering Book, in its discussions on automation, states:

“Automation implemented as code ensures that environments are consistent, repeatable, and less prone to human error.”

The SRE Workbook expands on this concept:

“Infrastructure as Code allows services to scale and evolve reliably by ensuring that configuration and infrastructure changes are automated and version-controlled.”

IaC is fundamental to:

Reducing toil

Increasing reliability

Enabling consistent automation across environments

Reducing configuration drift

Why the other options are incorrect:

A SRE supports testing in production; it does not ban automated tests.

C Using unsigned artifacts violates security and reliability best practices.

D Adding hardware is not an automation principle and contradicts efficiency goals.

Thus, the correct answer is B.

Comprehensive and Detailed Explanation From Exact Extract:

Google’s SRE approach emphasizes a blameless postmortem culture as a core learning mechanism. After a major outage, SRE teams conduct structured analyses to understand the root causes, contributing factors, and systemic weaknesses. The SRE Book defines this culture explicitly: “Postmortems are written analyses following incidents, designed to capture what happened, why it happened, and how to prevent the issue from recurring.” (SRE Book – Chapter: Postmortem Culture). This learning-focused approach reduces blame, increases resilience, and improves future reliability.

Option C aligns exactly with this principle.

Option A (follow-up culture) is vague and not an SRE term.

Option B (major incident culture) refers to incident handling, not learning afterward.

Option D (problem culture) is unrelated to SRE’s structured post-incident learning.

Thus, C is correct.

Comprehensive and Detailed Explanation From Exact Extract:

Service Level Indicators (SLIs) provide the quantitative measurements needed to determine how much of the Service Level Objective (SLO) has been consumed. Since the error budget is defined as the allowable amount of unreliability, SLI data is the source of truth for calculating how much of that budget remains.

From the Site Reliability Engineering Book, Chapter “Service Level Objectives”:

“SLIs provide the measurements used to determine compliance with SLOs. Error budgets are computed directly from the SLI measurements over the defined time window.”

The SRE Workbook further explains:

“Error budgets quantify the inverse of SLO performance. SLIs provide the raw data that allow teams to calculate how much of the budget has been consumed and how much remains.”

Thus, SLI data is the Only mechanism that determines remaining error budget.

Therefore, the statement is True.

Comprehensive and Detailed Explanation From Exact Extract:

SRE strengthens DevOps by adding reliability engineering, SLOs, error budgets, and production-focused automation. One key improvement is that the CI/CD pipeline extends safely into production using automated, tested, reliable deployment mechanisms.

The Site Reliability Engineering Book, “Release Engineering” chapter states:

“SRE complements DevOps by creating safe pathways for automated production deployments through engineering practices such as canarying, automation, and release gates.”

The SRE Workbook adds:

“SRE helps mature DevOps pipelines so they can operate safely in production, enabling continuous delivery to reach all the way through deployment.”

Why the other options are incorrect:

B SRE makes CD more necessary, not redundant

C SRE does not replace DevOps engineers

D IaC does not require moving to the cloud

Thus, the correct answer is A.

Comprehensive and Detailed Explanation From Exact Extract:

Google defines SRE as “what happens when you ask a software engineer to design an operations function.” (SRE Book – Introduction). The core engineering approach in SRE focuses on:

Eliminating toil

Building scalable systems

Applying software engineering to operational challenges

Learning from previous solutions and patterns

The SRE Book emphasizes: “SREs focus on designing and engineering solutions that reduce manual operations and scale service delivery.” (Chapter: Eliminating Toil). This aligns directly with Option B: designing a solution to eliminate toil and scale service delivery, informed by prior successful engineering patterns.

Option A focuses only on automating a single tuning activity—not holistic engineering.

Option C describes deployment, not engineering approach to operations.

Option D is about incident response, not engineering strategy.

Thus, B is the best representation of SRE’s engineering approach.

Comprehensive and Detailed Explanation From Exact Extract:

Using verified and signed artifacts is essential for safe automation, ensuring that deployments are consistent and free of dependency or supply chain errors. This is a fundamental principle in Google’s release engineering and SRE practices.

The Site Reliability Engineering Book, chapter “Release Engineering,” states:

“Releases should be built once, tested, signed, and stored in a secure repository. Only signed and verified artifacts should be promoted to production to prevent configuration drift and dependency inconsistencies.”

The SRE Workbook echoes this:

“Automated promotions depend on the integrity and immutability of artifacts. Signed artifacts ensure consistency and prevent errors related to mismatched dependencies.”

Why the other options are incorrect:

A External visibility is irrelevant and may create security risks.

C Error budgets relate to reliability, not artifact promotion.

D SLOs do not define artifact signing; this is handled by release engineering processes.

Thus, the correct answer is B.

Comprehensive and Detailed Explanation From Exact Extract:

Known workarounds represent toil that has no enduring value, one of the key characteristics of toil defined by the SRE framework.

From the Site Reliability Engineering Book, Chapter “Eliminating Toil”:

“Toil is work that is manual, repetitive, automatable, tactical, has no enduring value, and scales linearly with service size.”

Known workarounds fit this definition because:

They solve the same recurring problems repeatedly

They do not permanently fix the underlying issue

They consume engineer time without contributing long-term improvements

These activities lack enduring value and should be eliminated through automation or engineering fixes.

Why the other options are incorrect:

A. Linear scaling — Many forms of toil scale linearly, but this does not specifically describe workarounds.

B. Tactical — Tactical means short-term, but not all tactical work is a workaround.

C. Automatable — While some workarounds can be automated, not all are.

D. No enduring value — This is the defining trait of workaround-type toil.

Therefore, option D is correct.