Google Cloud Professional Cloud Architect Managing Implementation and Reliability Operations Flashcards

24 sample cards from the Managing Implementation and Reliability Operations deck

Sampled from the end of the deck, so these are different cards from the ones shown on the syllabus page.

1. What is an error budget and how is it calculated from an SLO?

   The error budget is the allowed amount of unreliability: 100% minus the SLO target. For a 99.9% SLO, the error budget is 0.1% of requests/time that may fail before the objective is breached.

2. What is an error budget policy and what typically happens when the budget is exhausted?

   It is an agreed policy governing actions based on error budget consumption. When the budget is exhausted, teams typically freeze new feature releases and prioritize reliability work until the budget recovers.

3. Roughly how much downtime per month does a 99.9% (three nines) availability SLO permit?

   About 43.2 minutes per 30-day month (approximately 8.76 hours per year).

4. What is the difference between horizontal and vertical scaling (scale out vs. scale up)?

   Horizontal scaling (scale out) adds more instances/machines to share load; vertical scaling (scale up) increases the resources (CPU/RAM) of a single instance.

5. What is a Managed Instance Group (MIG) and how does it enable autoscaling?

   A MIG is a group of identical VM instances created from a template. Its autoscaler automatically adds or removes instances based on metrics like CPU utilization, load balancing capacity, or custom metrics.

6. What are the main types of Google Cloud Load Balancers and a key distinction between them?

   Global external HTTP(S), SSL Proxy, and TCP Proxy load balancers (Layer 7 / proxy, global), versus regional external/internal Network (TCP/UDP) pass-through load balancers (Layer 4). HTTP(S) LBs route by content/URL; Network LBs forward by IP protocol/port.

7. What is the difference between a global and a regional load balancer in Google Cloud?

   A global load balancer (e.g., external HTTP(S)) uses a single anycast IP to route users to the nearest healthy backend across regions; a regional load balancer serves backends within one region only.

8. What is a health check in the context of load balancing and autoscaling?

   A periodic probe that determines whether a backend instance is healthy and able to serve traffic; unhealthy instances are removed from rotation (and, with autohealing, recreated).

9. What is a quota in Google Cloud and what are the two main quota types?

   A quota limits resource consumption to protect against runaway usage. Two types: rate quotas (requests per time period, e.g., API calls/minute) and allocation quotas (number of resources, e.g., VMs per region).

10. What is throttling (rate limiting) and how should a client respond to a 429 'Too Many Requests' / 'RESOURCE_EXHAUSTED' error?

    Throttling rejects requests exceeding a rate limit to protect a service. Clients should back off and retry later using exponential backoff with jitter rather than retrying immediately.

11. What is the difference between a cache hit and a cache miss, and how is hit ratio defined?

    A cache hit is when requested data is found in the cache; a miss is when it must be fetched from the origin. Hit ratio = cache hits / (cache hits + cache misses).

12. Compare cache-aside (lazy loading) vs. write-through caching strategies.

    Cache-aside: app loads data into cache only on a miss (lazy), risking stale data but caching only what's used. Write-through: data is written to cache and datastore simultaneously on every write, keeping cache fresh but adding write latency.

13. What is TTL (time to live) in caching and what trade-off does it control?

    TTL is the duration a cached item remains valid before expiring. It trades freshness against load: short TTL = fresher data but more origin hits; long TTL = fewer origin hits but staler data.

14. What is Cloud CDN and what does it cache?

    Cloud CDN uses Google's global edge network to cache content (typically static/cacheable HTTP responses) close to users, reducing latency and backend load; it works with the external HTTP(S) Load Balancer.

15. What is Memorystore in Google Cloud and what is it used for?

    Memorystore is a fully managed in-memory data store service for Redis and Memcached, used for low-latency caching and session storage.

16. What is graceful degradation as a failure-handling strategy?

    Designing a system to continue providing reduced/partial functionality (e.g., serving cached or default content) when a dependency fails, instead of failing completely.

17. What is autohealing in a Managed Instance Group?

    A self-healing mechanism where the MIG uses application-level health checks to detect and automatically recreate (replace) instances that are unresponsive or failing.

18. What is the bulkhead pattern in resilient system design?

    Isolating resources (e.g., connection pools, thread pools) per dependency or tenant so that a failure or overload in one part cannot exhaust resources and cascade to take down the whole system.

19. What is a dead-letter queue (topic) in Pub/Sub and why is it used?

    A separate topic where messages that repeatedly fail processing (exceed max delivery attempts) are routed, preventing them from blocking the subscription and allowing later inspection/reprocessing.

20. What is the difference between MTTR and MTBF in reliability operations?

    MTBF (Mean Time Between Failures) measures average uptime between failures (reliability); MTTR (Mean Time To Repair/Recover) measures average time to restore service after a failure (recoverability).

21. What is a canary deployment and how does it reduce risk?

    A release strategy that routes a small percentage of traffic to the new version first, monitoring it for errors before gradually shifting all traffic—limiting blast radius if the new version is faulty.

22. What is the difference between a blue-green deployment and a rolling update?

    Blue-green keeps two full environments and switches traffic from old (blue) to new (green) at once, enabling instant rollback. A rolling update incrementally replaces instances of the old version with the new one, with no second full environment.

23. What is a 'golden signal' in SRE monitoring, and what are the four golden signals?

    Golden signals are the key metrics to monitor a user-facing system: Latency, Traffic, Errors, and Saturation.

24. What is log-based metrics in Cloud Logging?

    Metrics derived from the content of log entries (counter or distribution types), letting you create metrics and alerts from log data—e.g., counting occurrences of a specific error message.

What this deck covers

Managing Implementation and Reliability Operations flashcards FAQ