Cloud
GCP interview questions on Compute Engine, Cloud Storage, BigQuery, Pub/Sub, and Vertex AI for data and ML workloads.
Commonly asked at: Commonly asked at cloud-native product companies and startups using GCP, such as Spotify-style scale-ups and companies migrating from AWS — general pattern, not company-verified.
Company names below are mentioned only to indicate the general type/level of interview these questions are common at, based on widely known industry patterns. This content is not affiliated with, endorsed by, or sourced from any confidential material of the named companies. All trademarks belong to their respective owners.
What is GCP, and what are its core service categories?
Tip: Name one flagship service per category — it shows breadth without rambling.
GCP is Google's cloud platform covering compute, storage, databases, networking, and AI/ML tools. Core services include Compute Engine for VMs, Cloud Storage for objects, BigQuery for analytics, and Cloud Functions or Cloud Run for serverless workloads.
Compute Engine vs Cloud Run vs Cloud Functions — what's the difference?
Tip: Rank them by "how much infrastructure you manage" — that framing makes the comparison intuitive.
Compute Engine gives full VMs you manage yourself — most control, most responsibility. Cloud Run runs containers and scales automatically, including to zero, without managing servers. Cloud Functions runs individual functions in response to events — the smallest serverless unit, with no container to manage at all.
What is BigQuery used for?
Tip: Mention the billing model — pay per data scanned — it's a commonly asked follow-up detail.
BigQuery is GCP's serverless data warehouse for running fast SQL queries over huge datasets — terabytes to petabytes. It separates storage and compute, so you're billed based on data scanned per query rather than a fixed server cost, and it's commonly used for analytics and BI.
What is Cloud IAM, and why does it matter?
Tip: Mention "principle of least privilege" explicitly — it's a phrase interviewers listen for.
Cloud IAM controls who can do what on which GCP resources, based on the principle of least privilege. You assign roles — collections of permissions — to users, groups, or service accounts at the project, folder, or resource level, and misconfigured IAM is one of the most common causes of cloud security incidents.
Cloud Storage vs Persistent Disk — what's the difference?
Tip: Say "object storage vs block storage" — that phrase is the core of the expected answer.
Cloud Storage is object storage — for files like images, backups, or logs, accessed over the network, built for durability and scale. Persistent Disk is block storage attached directly to a VM, behaving like a regular hard drive that the OS reads and writes to directly.
What is a VPC in Google Cloud?
Tip: Mention firewall rules and subnets — those two concepts usually come up as follow-ups.
A VPC is a private, isolated network within GCP where you launch resources like VMs and control traffic with firewall rules and subnets. You can design your own IP ranges and connect on-prem networks via VPN or Interconnect.
Project vs folder vs organization — what's the difference?
Tip: Describe it as a hierarchy, top-down — organization → folder → project — that framing is the clearest.
A project is the base unit for billing, APIs, and resource management. Folders group multiple projects, often by team or environment, and an organization sits at the top representing the whole company. Permissions and policies cascade down through this hierarchy.
What is autoscaling, and how does it work with Compute Engine?
Tip: Name the trigger metrics — CPU utilization, request rate — it's a common follow-up detail.
Autoscaling automatically adjusts the number of VM instances in a managed instance group based on load, like CPU utilization or request rate, adding instances as demand rises and removing them as it drops. This balances performance and cost without manual intervention.
What is Cloud CDN, and why would you use it?
Tip: Mention latency reduction and origin load reduction — those are the two main benefits to state.
Cloud CDN caches content at Google's edge locations closer to users, reducing latency and cutting down load on your origin servers. It's typically used for static assets, images, and content that doesn't change often, fronted by a global load balancer.
⭐ Scenario: Your application on GCP is experiencing unexpectedly high costs this month. How would you investigate?
Tip: This is scenario-based — mention specific GCP tools you'd actually open, not generic "check the bill" advice.
Situation: A GCP project's monthly bill spiked well above the usual baseline without an obvious feature launch to explain it.
Task: I needed to find which service was driving the cost increase and whether it was legitimate usage or a misconfiguration.
Action: I used the Billing Reports and Cost Table in the GCP console, broken down by service and SKU, and cross-checked it against Cloud Monitoring metrics to see if any service had an unusual spike in usage — like a runaway Cloud Function retry loop or an oversized, idle VM.
Result: I found a misconfigured autoscaler that never scaled back down after a traffic spike; fixing its scale-down policy brought costs back to the expected baseline.
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