Domain 1: Designing and Planning a Cloud Solution Architecture (~25%)

Domain 1 is the largest domain on the Professional Cloud Architect exam, accounting for roughly 25% of the questions (approximately 13-15 out of 50-60). This domain tests your ability to translate business requirements into technical cloud architectures, select the right GCP services for a given scenario, design migration plans, and plan for ongoing modernization. Unlike the ACE exam, which focuses on implementation, the PCA exam demands architectural decision-making -- you must justify why a particular service or pattern is the right choice, not just how to configure it.

1.1 Meeting Business Requirements and Strategy

The PCA exam presents scenario-based questions where a business describes its goals, and you must choose the architecture that best aligns with those goals. The exam tests your ability to balance cost, performance, reliability, compliance, and time-to-market.

Business Use Cases and Product Strategy

Exam scenarios typically fall into one of these patterns:

Exam trap: The exam frequently presents scenarios where the "most technically elegant" solution is not the right answer. A startup that needs to launch in 2 weeks should rehost to Compute Engine, not spend months re-architecting for GKE. Always match the solution to the business constraint -- budget, timeline, team expertise, and compliance requirements.

Cost Optimization Strategies

Cost optimization is a dominant theme across the entire PCA exam. You must know the full discount hierarchy and when each applies.

Discount Types Comparison

Discount priority order: CUDs take precedence over SUDs. A resource covered by a CUD does not also receive SUDs. Spot/preemptible VMs are not eligible for SUDs or CUDs.

Exam trap: SUDs apply automatically -- you do not need to purchase them. They are only available for N1 and sole-tenant nodes. N2, N2D, E2, C2, C3, T2D, and Tau machine families are NOT eligible for SUDs. If the exam asks about automatic discounts for an E2 or N2 instance, the answer is "none" -- use CUDs instead. E2 instances are eligible for Flexible CUDs.

Additional Cost Optimization Techniques

TCO Analysis and ROI

The exam tests whether you understand Total Cost of Ownership beyond just compute pricing:

• Direct costs: Compute, storage, networking (egress), licensing
• Indirect costs: Operational overhead, staffing, training, downtime
• Migration costs: One-time costs for assessment, refactoring, data transfer, parallel running
• Ongoing optimization: Cost of continuous monitoring, right-sizing, and re-architecting

The Google Cloud Pricing Calculator is the primary tool for estimating costs. Migration Center provides TCO comparisons between on-premises and cloud.

Compliance and Observability

For compliance-heavy scenarios:

• VPC Service Controls: Create security perimeters around GCP resources to prevent data exfiltration
• Organization Policy Service: Enforce constraints (e.g., restrict resource locations to specific regions)
• Cloud Audit Logs: Admin Activity logs (always on), Data Access logs (configurable), System Event logs
• Access Transparency: Logs of Google staff accessing your data (for compliance audits)
• Assured Workloads: Preconfigured compliance environments for FedRAMP, HIPAA, CJIS, etc.

1.2 Defining Technical Requirements

High Availability Design Patterns

HA is a core PCA topic. You must understand the availability implications of different deployment topologies.

Exam trap: Multi-zone is NOT the same as multi-region. A regional MIG spans multiple zones within a single region, giving you zone-level resilience. For region-level failures (extremely rare but testable), you need multi-region deployment with global load balancing.

Load Balancer Selection Guide

The PCA exam heavily tests load balancer selection. You must match the scenario to the correct load balancer type.

Decision tree for the exam:

1. Is it HTTP/HTTPS traffic? --> Application Load Balancer (Layer 7)
2. Is it internal-only? --> Internal variant
3. Does it need global reach? --> Global variant (requires Premium Network Tier)
4. Is it non-HTTP TCP/UDP? --> Network Load Balancer (Layer 4)
5. Do you need to preserve client source IP for non-HTTP? --> Passthrough Network LB
6. Do you need SSL offload for non-HTTP TCP? --> Proxy Network LB

Exam trap: Cloud Armor DDoS protection and Cloud CDN integration are only available with the Global External Application Load Balancer. If a scenario requires WAF rules or DDoS protection, the answer is always this load balancer type. Internal load balancers do NOT support Cloud Armor.

Autoscaling

Managed Instance Groups (MIGs)

Managed Instance Groups are the primary compute scaling mechanism:

GKE Autoscaling

Exam trap: HPA and VPA should not be used together on the same metric (e.g., both scaling on CPU). They will conflict. Use MPA if you need both horizontal and vertical scaling.

Serverless Services Comparison

Exam trap: Cloud Run is the recommended default serverless platform for new workloads. Cloud Functions is for event-driven glue code (Pub/Sub triggers, Cloud Storage triggers). App Engine Standard is legacy but still tested. App Engine Flexible does NOT scale to zero -- if cost optimization is the priority and the workload is bursty, App Engine Flexible is the wrong answer.

Google Cloud Well-Architected Framework

The Well-Architected Framework consists of six pillars. The PCA exam tests your understanding of design principles from each pillar.

Five foundational design principles across all pillars:

1. Design for change -- Small, frequent deployments with rapid feedback loops
2. Document your architecture -- Link documentation to design decisions
3. Simplify and use managed services -- Reduce operational burden
4. Decouple architecture -- Separate components for independent operation
5. Use stateless architecture -- Improve scalability via shared storage and caching

1.3 Choosing GCP Network, Storage, and Compute Resources

Storage and Database Decision Tree

Choosing the right storage service is one of the most frequently tested areas. Use this decision matrix.

Relational Databases

Exam trap: If the scenario requires global strong consistency with a relational database, the answer is always Spanner. Cloud SQL cannot provide multi-region strong consistency. AlloyDB is PostgreSQL-compatible but does not offer Spanner's horizontal scaling or global distribution.

NoSQL Databases

Exam trap: Bigtable is NOT a good choice for data smaller than 1 TB -- the minimum node count makes it expensive at small scale. For small-to-medium NoSQL workloads, Firestore is the right answer. Bigtable excels at high-throughput, low-latency reads/writes at massive scale (petabytes).

Analytics and Data Warehousing

BigQuery is the default answer for analytics workloads. Key features: federated queries (query data in Cloud Storage, Bigtable, or external sources without loading), materialized views, ML (BigQuery ML), streaming inserts, and partitioning/clustering for cost optimization.

Object and File Storage

Compute Decision Tree

Machine Family Quick Reference

Networking Services

VPC Fundamentals

A VPC network is a global resource containing regional subnets. Key concepts:

Exam trap: VPC Peering is NOT transitive. If VPC-A peers with VPC-B, and VPC-B peers with VPC-C, VPC-A cannot reach VPC-C through VPC-B. For transitive connectivity, use a hub-and-spoke model with Network Connectivity Center or a Shared VPC. Network Connectivity Center is the answer when the exam describes multi-VPC or multi-cloud architectures needing transitive routing through a central hub.

Hybrid Connectivity

Decision criteria:

• Need < 3 Gbps and can tolerate internet-based latency? --> Cloud VPN
• Need > 10 Gbps and have colocation access? --> Dedicated Interconnect
• Need > 3 Gbps but no colocation? --> Partner Interconnect
• Need encrypted connectivity over Interconnect? --> Use VPN over Interconnect (HA VPN tunnels over Dedicated/Partner Interconnect)

Exam trap: Cloud VPN traffic is encrypted (IPsec). Dedicated and Partner Interconnect traffic is NOT encrypted by default -- it traverses Google's network but is not IPsec-encrypted. If the scenario requires encryption over Interconnect, the answer is to layer HA VPN tunnels over the Interconnect connection.

Additional Networking Services

1.4 Designing a Migration Plan

Migration Phases

Google Cloud defines a four-phase migration framework:

Migration Approaches

Exam trap: The exam loves scenarios where a company says "we want to move to the cloud as fast as possible" -- the answer is almost always rehost first, then modernize later. Re-architecting is the right long-term play but never the fastest path. Conversely, if the scenario emphasizes "we want to take full advantage of cloud-native capabilities," rehosting is the wrong answer.

Migration Tools

Dependency and License Analysis

Before migration, you must understand:

• Application dependencies: Which applications talk to which? Map with Migration Center or manual discovery.
• Database dependencies: Which apps share databases? Foreign key relationships across schemas?
• Network dependencies: What ports and protocols are required? Firewall rule translation?
• License portability: Can existing licenses (Oracle, SQL Server, Windows) be brought to GCP? Do you need new cloud licenses? Sole-tenant nodes may be required for bring-your-own-license (BYOL) scenarios where license terms require physical host isolation.

Exam trap: Oracle Database licensing on Google Cloud often requires sole-tenant nodes because Oracle licenses per physical core, not per vCPU. If the exam describes an Oracle Database migration, sole-tenant nodes are likely part of the correct answer.

1.5 Planning for Future Improvements

Cloud Modernization Journey

The PCA exam tests your understanding of the modernization progression:

VMs (Compute Engine)
  --> Containers (GKE)
    --> Managed Containers (Cloud Run)
      --> Microservices + Service Mesh (GKE + Anthos Service Mesh)
        --> Event-Driven / Serverless (Cloud Functions + Pub/Sub + Eventarc)

Each step increases cloud-native optimization but also increases refactoring effort:

Integration with AI/ML via Vertex AI

Vertex AI is Google Cloud's unified ML platform. The PCA exam tests high-level architectural decisions:

Exam trap: The exam may present scenarios where a company wants ML capabilities but has no data science team. The answer is typically AutoML (no-code) or pre-trained APIs (Vision AI, Natural Language AI, Translation AI), not custom Vertex AI Training.

Data Mesh and BigQuery Federation

For data-heavy architectures, the PCA exam tests:

• BigQuery federated queries: Query data in Cloud Storage (Parquet, ORC, Avro, CSV), Bigtable, or Cloud SQL without loading it into BigQuery. Trade-off: higher query latency but no ETL pipeline needed.
• BigQuery Omni: Run BigQuery analytics on data stored in AWS S3 or Azure Blob Storage without moving it.
• Analytics Hub: Share BigQuery datasets across organizations with governed access.
• Dataplex: Data governance and management across data lakes and data warehouses; auto-discovery, metadata management, data quality.
• Data mesh principles: Domain-oriented decentralized data ownership, data as a product, self-serve data infrastructure, federated computational governance.

Exam Strategy for Domain 1

Question Patterns

1. "Which service should you use?" -- Map the requirements (scale, consistency, latency, cost) to the correct service using the decision trees above.
2. "How should you minimize cost?" -- Apply the discount hierarchy: Spot VMs > CUDs > SUDs > right-sizing > serverless.
3. "How should you design for high availability?" -- Match the availability requirement to multi-zone, multi-region, or hybrid.
4. "What migration approach should you use?" -- Match the business constraint (speed, budget, team skill) to rehost/replatform/refactor.
5. "Which load balancer?" -- Follow the decision tree: HTTP vs. TCP, internal vs. external, global vs. regional.

Common Exam Traps Summary

References

• Google Cloud Well-Architected Framework
• Cloud Load Balancing Overview
• Migration to Google Cloud: Getting Started
• Preemptible and Spot VMs
• Sustained Use Discounts
• Committed Use Discounts Overview
• VPC Overview
• Choosing a Network Connectivity Product
• Compute Engine Machine Families
• Google Cloud Database Products
• Migration Center
• Google Cloud Pricing Calculator
• Vertex AI Documentation
• BigQuery Documentation
• GKE Autoscaling
• Cloud Run Documentation
• Cloud Functions Documentation
• VMware Engine