Google Cloud Platform

GCP is Google's suite of cloud infrastructure and managed services. This skill covers architecture decisions, service selection, and implementation patterns for the most commonly used GCP building blocks: compute (Cloud Run, GKE, Cloud Functions), data (BigQuery, Cloud Storage, Pub/Sub), and databases (Cloud SQL, Firestore, Spanner, Bigtable). The emphasis is on choosing the right service for the problem and configuring it correctly rather than memorizing every API surface.

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When to use this skill

Trigger this skill when the user:

• Deploys a containerized service or API to GCP
• Designs a data pipeline (ingestion, transformation, analytics)
• Needs to choose between GCP database offerings (Cloud SQL, Firestore, Spanner, Bigtable)
• Sets up IAM roles, service accounts, or Workload Identity
• Architects an event-driven system with Pub/Sub and Cloud Functions
• Configures networking (VPC, Load Balancer, Cloud CDN, Cloud Armor)
• Estimates or controls GCP costs (BigQuery slot reservations, Cloud Run concurrency)

Do NOT trigger this skill for:

• AWS or Azure architecture (use the corresponding cloud skill)
• Application-level code that happens to run on GCP but has no GCP-specific concerns

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Key principles

1. Managed services first - Prefer fully managed services (Cloud Run, BigQuery, Firestore) over self-managed ones (GCE with custom installs). The operational overhead of managing VMs, patches, and scaling is rarely worth the flexibility.

2. BigQuery is the analytics layer - BigQuery is GCP's default for any analytical workload at any scale. It is serverless, cost-effective for infrequent queries, and integrates with Dataflow, Pub/Sub, and Looker. Use it unless you need sub-second OLTP latency.

3. Cloud Run is the default compute - For HTTP-serving workloads, Cloud Run (not GKE, not App Engine) is the right default. It is stateless, auto-scales to zero, and charges per request-second. Move to GKE only when you need persistent connections, GPUs, or complex networking.

4. Pub/Sub for decoupling - Whenever two services need to communicate asynchronously, route through Pub/Sub. It provides durable delivery, at-least-once semantics, replay, and dead-letter queues without you managing a broker.

5. IAM at project level, fine-grained at resource level - Grant roles at the lowest resource scope possible. Use service accounts with Workload Identity for workloads running on GCP - never create and download service account key files.

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Core concepts

Resource hierarchy

Organization
  └── Folders (teams, environments)
        └── Projects  <-- primary billing and IAM boundary
              └── Resources (Cloud Run services, BigQuery datasets, buckets, etc.)

IAM policies are inherited downward. A role granted at the organization level applies to all projects. Grant permissions at the project or resource level to limit blast radius.

IAM model

Every GCP principal (user, service account, group) is granted roles, which are bundles of permissions. There are three role types:

Type	Example	When to use
Basic	roles/viewer, roles/editor	Never in production - too broad
Predefined	roles/run.invoker, roles/bigquery.dataViewer	Default choice
Custom	Built from individual permissions	When predefined is still too broad

Service accounts are identities for workloads. Use Workload Identity to bind a Kubernetes service account to a GCP service account - no key files needed.

Compute spectrum

Service	Trigger	State	Scale to zero	Use case
Cloud Functions (gen2)	Event / HTTP	Stateless	Yes	Lightweight event handlers
Cloud Run	HTTP / gRPC	Stateless	Yes	Containerized APIs, backends
GKE Autopilot	Always-on	Stateful OK	No	Long-running, GPU, complex networking
Compute Engine	Always-on	Stateful	No	VMs, custom OS, legacy lift-and-shift

Storage and database tiers

Service	Model	Sweet spot
Cloud Storage	Object / blob	Files, backups, data lake raw zone
BigQuery	Columnar OLAP	Analytics, reporting, ad-hoc queries
Cloud SQL	Relational (Postgres/MySQL)	OLTP, existing SQL apps
Firestore	Document (NoSQL)	Mobile/web, hierarchical, real-time sync
Spanner	Globally distributed relational	Finance, inventory, global consistency
Bigtable	Wide-column NoSQL	Time-series, IoT, >1 TB key-value
Memorystore	Redis / Memcached	Caching, session storage, leaderboards

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Common tasks

Deploy a containerized service to Cloud Run

# Build and push image to Artifact Registry
gcloud builds submit --tag us-central1-docker.pkg.dev/PROJECT/REPO/my-service:latest

# Deploy with recommended production settings
gcloud run deploy my-service \
  --image us-central1-docker.pkg.dev/PROJECT/REPO/my-service:latest \
  --region us-central1 \
  --platform managed \
  --service-account my-service-sa@PROJECT.iam.gserviceaccount.com \
  --set-env-vars "ENV=production" \
  --memory 512Mi \
  --cpu 1 \
  --concurrency 80 \
  --max-instances 10 \
  --no-allow-unauthenticated   # use --allow-unauthenticated for public APIs

Key dials:

• --concurrency - requests handled per container instance (default 80). Lower it for CPU-bound work; increase for I/O-bound.
• --max-instances - hard cap to control costs and protect downstream services.
• --no-allow-unauthenticated + roles/run.invoker on the calling service account is the correct pattern for service-to-service calls.

Design a data pipeline

Standard GCP data pipeline pattern:

Source (app events, CDC, files)
  --> Pub/Sub topic (ingestion buffer, durability)
  --> Dataflow job (transform, enrich, validate)
  --> BigQuery dataset (analytics layer)
  --> Looker / Looker Studio (visualization)

For simpler pipelines without transformation logic, use BigQuery subscriptions directly from Pub/Sub (no Dataflow needed). For batch ingestion from Cloud Storage, use BigQuery Data Transfer Service or a scheduled Dataflow pipeline.

Set up BigQuery for analytics

-- Create a dataset with a region and expiration
CREATE SCHEMA my_project.analytics
  OPTIONS (
    location = 'us-central1',
    default_table_expiration_days = 365
  );

-- Partition tables by date to control scan costs
CREATE TABLE analytics.events (
  event_id STRING,
  user_id  STRING,
  event_ts TIMESTAMP,
  payload  JSON
)
PARTITION BY DATE(event_ts)
CLUSTER BY user_id;

-- Use partition filters to avoid full-table scans
SELECT user_id, COUNT(*) as cnt
FROM analytics.events
WHERE DATE(event_ts) BETWEEN '2024-01-01' AND '2024-03-31'
GROUP BY user_id;

Cost control checklist:

• Always partition large tables by date/timestamp
• Cluster on high-cardinality filter columns (user_id, org_id)
• Use SELECT specific_columns not SELECT *
• Set column-level access policies on PII fields
• Monitor with INFORMATION_SCHEMA.JOBS to catch expensive queries

Choose the right database

Use this decision matrix:

Do you need SQL?
  YES -> Is global multi-region consistency required?
    YES -> Spanner
    NO  -> Cloud SQL (Postgres preferred)
  NO  -> Is data hierarchical / document-shaped?
    YES -> Is real-time sync or offline support needed?
      YES -> Firestore
      NO  -> Firestore (still fine) or BigQuery for analytics
    NO  -> Is it time-series / IoT at >1 TB scale?
      YES -> Bigtable
      NO  -> Cloud Storage (data lake) or BigQuery

Key differentiators:

• Cloud SQL caps at ~10 TB and one primary region - fine for most apps
• Spanner is 5-10x the cost of Cloud SQL; justify with global write requirements
• Firestore bills per operation, not compute - avoid heavy aggregation queries
• Bigtable has a minimum cost (~$0.65/hr per node); not worth it under 1 TB

Configure IAM with least privilege

# Create a service account for a Cloud Run service
gcloud iam service-accounts create my-service-sa \
  --display-name "my-service runtime SA"

# Grant only the permissions it needs
gcloud projects add-iam-policy-binding PROJECT \
  --member "serviceAccount:my-service-sa@PROJECT.iam.gserviceaccount.com" \
  --role "roles/bigquery.dataViewer"

gcloud projects add-iam-policy-binding PROJECT \
  --member "serviceAccount:my-service-sa@PROJECT.iam.gserviceaccount.com" \
  --role "roles/pubsub.publisher"

# For GKE: bind Kubernetes SA to GCP SA via Workload Identity
gcloud iam service-accounts add-iam-policy-binding my-service-sa@PROJECT.iam.gserviceaccount.com \
  --role "roles/iam.workloadIdentityUser" \
  --member "serviceAccount:PROJECT.svc.id.goog[NAMESPACE/KSA_NAME]"

Never create and download service account key JSON files for workloads running on GCP. Use Workload Identity for GKE, and the automatic metadata server for Cloud Run. Key files leak, expire, and are a primary source of GCP credential breaches.

Set up Cloud CDN and Load Balancer

For a Cloud Run service that needs CDN caching:

# Create a serverless NEG pointing at Cloud Run
gcloud compute network-endpoint-groups create my-service-neg \
  --region us-central1 \
  --network-endpoint-type serverless \
  --cloud-run-service my-service

# Create backend service and enable CDN
gcloud compute backend-services create my-service-backend \
  --global \
  --enable-cdn \
  --cache-mode CACHE_ALL_STATIC \
  --custom-response-header "Cache-Control:public, max-age=3600"

gcloud compute backend-services add-backend my-service-backend \
  --global \
  --network-endpoint-group my-service-neg \
  --network-endpoint-group-region us-central1

# Create URL map, target proxy, and forwarding rule
# (typically done via Terraform for production)

Use Cloud Armor on the backend service to add WAF rules and rate limiting at the edge. Attach Cloud CDN only to responses that are safe to cache - set Cache-Control: private on auth-gated endpoints.

Implement event-driven architecture with Pub/Sub and Cloud Functions

# Create a topic
gcloud pubsub topics create order-created

# Create a dead-letter topic for failed messages
gcloud pubsub topics create order-created-dlq

# Create a push subscription that triggers Cloud Functions (gen2)
gcloud pubsub subscriptions create order-created-sub \
  --topic order-created \
  --ack-deadline 60 \
  --dead-letter-topic order-created-dlq \
  --max-delivery-attempts 5

# Deploy a Cloud Function triggered by the topic
gcloud functions deploy process-order \
  --gen2 \
  --runtime nodejs20 \
  --trigger-topic order-created \
  --region us-central1 \
  --service-account processor-sa@PROJECT.iam.gserviceaccount.com \
  --set-env-vars "PROJECT_ID=PROJECT"

Pattern notes:

• Always configure a dead-letter topic - without one, a poison-pill message retries indefinitely and blocks the subscription.
• Set --ack-deadline to at least 2x your function's expected execution time.
• Use --max-delivery-attempts 5 with exponential backoff before DLQ.
• For high-throughput scenarios (>10k msg/s), use Dataflow instead of Functions.

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Anti-patterns / common mistakes

Mistake	Why it's wrong	What to do instead
Downloading service account key files	Credentials that leak, don't auto-rotate, and are hard to audit	Use Workload Identity (GKE) or the metadata server (Cloud Run)
SELECT * on large BigQuery tables	Scans entire table regardless of filters, costs multiply	Select only needed columns; partition + cluster the table
No dead-letter topic on Pub/Sub subscriptions	Poison-pill messages block the subscription indefinitely	Always configure a DLQ with --max-delivery-attempts
Spanner for a single-region OLTP app	5-10x the cost of Cloud SQL with no benefit	Use Cloud SQL (Postgres) unless global writes are required
Granting roles/editor to a service account	Overly broad; can read/write all project resources	Grant narrowest predefined role needed; use custom roles if required
Cloud Run without max-instances	Unexpected traffic spike can exhaust downstream DB connections	Always set --max-instances and size connection pools accordingly

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Gotchas

1. Cloud Run without max-instances is a database killer - Cloud Run scales to hundreds of instances on traffic spikes. Each instance holds its own connection pool. Without --max-instances, a traffic spike can open thousands of database connections and exhaust Cloud SQL or Spanner limits. Always set --max-instances and size --concurrency to match your downstream connection budget.

2. BigQuery charges for scanned bytes, not returned rows - A SELECT * on a 10 TB table bills for 10 TB even if you filter to one row. Always select only the columns needed and add partition filter clauses. Without a WHERE DATE(event_ts) BETWEEN ... condition on a partitioned table, the query scans all partitions.

3. Pub/Sub without a dead-letter topic blocks the subscription - A single malformed message that causes the consumer to throw an exception will be retried indefinitely (up to --max-delivery-attempts, but that defaults to unlimited without a DLQ configured). Always set --dead-letter-topic and --max-delivery-attempts together - one without the other provides incomplete protection.

4. Service account key files are a persistent credential leak vector - Downloaded JSON key files don't expire, are easy to commit to git, and can't be audited as precisely as Workload Identity. GCP's metadata server and Workload Identity provide automatic, rotating credentials for every compute surface. Never create key files for workloads that run on GCP infrastructure.

5. Firestore billing on aggregation queries - Firestore bills per document read. A query that counts documents in a collection reads every document to compute the count. At scale, this means SELECT COUNT(*) equivalents are extremely expensive. Maintain aggregation counters as separate documents and update them via Cloud Functions triggered on writes.

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References

For detailed patterns and reference tables on specific GCP topics, read the relevant file from the references/ folder:

• references/service-map.md - quick lookup of use case to GCP service

Only load a references file if the current task requires it - they add context length.