The Google Professional Cloud Developer exam tests your ability to build and deploy scalable, secure, cloud-native applications on Google Cloud. Unlike infrastructure certifications, this one goes deep on application code patterns, managed services for developers, CI/CD pipelines, and observability — the kind of knowledge that separates a developer who uses GCP from one who actually knows it.
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Cloud-native applications are designed around the 12-factor methodology: codebase in version control, explicit dependencies, config in environment, backing services as attached resources, separate build/release/run stages, stateless processes, port binding, concurrency via process model, disposability (fast startup, graceful shutdown), dev/prod parity, logs as event streams, admin processes as one-off tasks. Microservices on GCP: Cloud Run (serverless containers, request-driven scaling), GKE (managed Kubernetes for complex workloads), App Engine (fully managed, language-specific runtimes). Service communication: REST over HTTP/S (Cloud Endpoints + OpenAPI), gRPC (Protocol Buffers, bidirectional streaming), Pub/Sub (async messaging for decoupling services).
Choosing the right storage: Firestore (document DB, real-time sync, serverless, for user-facing data with flexible schema), Cloud Spanner (horizontally scalable relational DB with global ACID transactions, for financial or inventory systems), Bigtable (wide-column, time-series and IoT workloads at petabyte scale), Cloud SQL (managed PostgreSQL/MySQL/SQL Server for existing relational workloads), Memorystore (managed Redis/Memcached for caching). Cloud Storage: object storage with four storage classes (Standard, Nearline, Coldline, Archive) for cost optimisation. Object lifecycle management automates transitions between classes. Signed URLs grant time-limited access to private objects — generated server-side and passed to clients for direct upload/download.
Cloud Build: managed CI/CD with cloudbuild.yaml steps. Each step is a container that runs a command — flexibility to use any tool. Triggers connect Cloud Build to Cloud Source Repositories, GitHub, or Bitbucket. Artifact Registry stores container images and language packages (Maven, npm, Python). Cloud Deploy: managed continuous delivery to GKE, Cloud Run, or GKE Autopilot. Delivery pipelines define promotion sequences (dev > staging > prod) with optional approval gates and canary/blue-green strategies. Rollback is one command: gcloud deploy rollouts rollback. Cloud Code: IDE plugins (VS Code, JetBrains) for local Kubernetes development. Skaffold automates build-push-deploy on file save. Container Structure Tests validate image contents without running the container.
Application security: Secret Manager for storing and rotating credentials (not environment variables for secrets). Workload Identity Federation: GKE workloads can assume GCP service account identities without key files. Binary Authorization: policy-enforced admission control that requires container images to be signed by trusted attestors before deployment. Observability: Cloud Monitoring (metrics, uptime checks, alerting policies), Cloud Logging (structured logs via the Logging client libraries, Log-based metrics), Cloud Trace (distributed tracing, latency analysis), Cloud Profiler (continuous CPU/memory profiling in production). Use OpenTelemetry for vendor-neutral instrumentation. Cloud Endpoints and Apigee: Endpoints (lightweight API management, OpenAPI or gRPC, authentication via JWT or API key), Apigee (enterprise API gateway with rate limiting, monetisation, analytics, and developer portal).
Firestore supports SQL joins and relational queries like Cloud SQL does
Firestore is not a relational database — it cannot do joins; model data for your access patterns, not normalised
Cloud Run and App Engine are interchangeable container platforms
Cloud Run and App Engine both run containers but differ in control: Cloud Run is fully containerised, App Engine handles the runtime
Cloud Build handles both CI and CD all the way to production
Cloud Build is for CI (build and test); Cloud Deploy is for CD (promote through environments) — they complement each other
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