/cloud-solution-architect

Cloud Application Best Practices

Twelve best practices from the Azure Architecture Center for designing, building, and operating cloud applications.

1. API Design

Design RESTful web APIs that promote platform independence and loose coupling between clients and services.

Key Recommendations

• Organize APIs around resources using nouns, not verbs, in URIs
• Use standard HTTP methods (GET, POST, PUT, PATCH, DELETE) with correct semantics
• Use plural nouns for collection endpoints (e.g., /orders, /customers)
• Support HATEOAS to enable client navigation of the API without prior knowledge
• Design coarse-grained operations to avoid chatty request patterns
• Do not expose internal database structure through the API surface
• Version APIs to manage breaking changes without disrupting existing clients
• Return appropriate HTTP status codes and consistent error response bodies

WAF Pillar Alignment

Performance Efficiency · Operational Excellence

Common Mistakes

• Using verbs in URIs (e.g., /getOrders) instead of resource-based paths
• Exposing database schema directly through API contracts
• Creating chatty APIs that require multiple round-trips for a single logical operation

2. API Implementation

Implement web APIs to be efficient, responsive, scalable, and available for consuming clients.

Key Recommendations

• Make actions idempotent so retries are safe (especially PUT and DELETE)
• Support content negotiation via Accept and Content-Type headers
• Follow the HTTP specification for status codes, methods, and headers
• Handle exceptions gracefully and return meaningful error responses
• Support resource discovery through links and metadata
• Limit and paginate large result sets to minimize network traffic
• Handle large requests asynchronously using 202 Accepted with status polling
• Compress responses where appropriate to reduce payload size

WAF Pillar Alignment

Operational Excellence

Common Mistakes

• Not handling large requests asynchronously, causing timeouts
• Not minimizing network traffic through pagination, filtering, or compression

3. Autoscaling

Dynamically allocate and deallocate resources to match performance requirements while optimizing cost.

Key Recommendations

• Use Azure Monitor autoscale and built-in platform autoscaling features
• Scale based on metrics that directly correlate with load (CPU, queue length, request rate)
• Combine schedule-based and metric-based scaling for predictable traffic patterns
• Set appropriate minimum, maximum, and default instance counts
• Configure scale-in rules as carefully as scale-out rules
• Use cooldown periods to prevent oscillation (flapping)
• Plan for the delay between triggering a scale event and resources becoming available

WAF Pillar Alignment

Performance Efficiency · Cost Optimization

Common Mistakes

• Not setting appropriate minimum and maximum limits for scaling
• Not considering scale-in behavior, leading to premature resource removal
• Using metrics that do not accurately reflect application load

4. Background Jobs

Implement batch processing, long-running tasks, and workflows as background jobs decoupled from the user interface.

Key Recommendations

• Use Azure platform services such as Functions, WebJobs, and Batch for hosting
• Trigger background jobs with events, schedules, or message queues
• Return results to calling tasks through queues, events, or shared storage
• Design jobs to be independently deployable, scalable, and versioned
• Handle partial failures and support safe restarts with checkpointing
• Monitor job health with logging, metrics, and alerting
• Implement graceful shutdown to allow in-progress work to complete

WAF Pillar Alignment

Operational Excellence

Common Mistakes

• Not handling failures or partial completion within long-running jobs
• Not monitoring background job health, missing silent failures

5. Caching

Copy frequently read, rarely modified data to fast storage close to the application to improve performance.

Key Recommendations

• Cache data that is read often but changes infrequently
• Use Azure Cache for Redis for distributed, high-throughput caching
• Set appropriate expiration policies (TTL) to balance freshness and hit rates
• Handle cache misses gracefully with a cache-aside pattern
• Address concurrency issues when multiple processes update the same cached data
• Implement cache invalidation strategies aligned with data change patterns
• Pre-populate caches for known hot data during application startup

WAF Pillar Alignment

Performance Efficiency

Common Mistakes

• Caching highly volatile data that expires before it can be served
• Not handling cache invalidation, serving stale data to users
• Cache stampede — many concurrent requests regenerating the same expired entry

6. CDN (Content Delivery Network)

Use CDNs to deliver static and dynamic web content efficiently to users from edge locations worldwide.

Key Recommendations

• Offload static assets (images, scripts, stylesheets) to the CDN to reduce origin load
• Configure appropriate cache-control headers for each content type
• Version static content via file names or query strings for reliable cache busting
• Use HTTPS and enforce TLS for secure delivery
• Plan for CDN fallback so the application degrades gracefully if the CDN is unavailable
• Handle deployment and versioning so users receive updated content promptly

WAF Pillar Alignment

Performance Efficiency

Common Mistakes

• Not versioning content, causing users to receive stale cached assets after deployments
• Setting improper cache headers, resulting in under-caching or over-caching

7. Data Partitioning

Divide data stores into partitions to improve scalability, availability, and performance while reducing contention and storage costs.

Key Recommendations

• Choose partition keys that distribute data and load evenly across partitions
• Use horizontal (sharding), vertical, or functional partitioning based on access patterns
• Minimize cross-partition queries to avoid performance degradation
• Design partitions to match the most common query patterns
• Plan for rebalancing as data volume and access patterns evolve
• Consider partition limits and throughput caps of the target data store
• Reduce contention and storage costs by separating hot and cold data

WAF Pillar Alignment

Performance Efficiency · Cost Optimization

Common Mistakes

• Creating hotspots by selecting a partition key with skewed distribution
• Not considering the cost and latency of cross-partition queries

8. Data Partitioning Strategies (by Service)

Apply service-specific partitioning strategies across Azure SQL Database, Azure Table Storage, Azure Blob Storage, and other data services.

Key Recommendations

• Shard Azure SQL Database to distribute data for horizontal scaling
• Design Azure Table Storage partition keys around query access patterns
• Organize Azure Blob Storage using virtual directories and naming conventions
• Align partition boundaries with the most frequent query predicates
• Reduce latency by co-locating related data within the same partition
• Monitor partition metrics and rebalance when skew is detected

WAF Pillar Alignment

Performance Efficiency · Cost Optimization

Common Mistakes

• Not aligning the partition strategy with actual query patterns, causing full scans
• Ignoring service-specific partition limits and throttling thresholds

9. Host Name Preservation

Preserve the original HTTP host name between reverse proxies and backend web applications to avoid issues with cookies, redirects, and CORS.

Key Recommendations

• Forward the original Host header from the reverse proxy to the backend
• Configure Azure Front Door, Application Gateway, and API Management for host preservation
• Ensure cookies are set with the correct domain matching the original host name
• Verify redirect URLs reference the external host name, not the internal backend address
• Test CORS configurations end-to-end with the preserved host name
• Document host name flow across all network hops in the architecture

WAF Pillar Alignment

Reliability

Common Mistakes

• Not preserving host headers, causing redirect loops or incorrect absolute URLs
• Breaking session cookies because the cookie domain does not match the forwarded host

10. Message Encoding

Choose the right payload structure, encoding format, and serialization library for asynchronous messages exchanged between distributed components.

Key Recommendations

• Evaluate JSON, Avro, Protobuf, and MessagePack based on performance and interoperability needs
• Use schema registries to enforce and version message contracts
• Validate incoming messages against their schemas before processing
• Prefer compact binary formats (Protobuf, Avro) for high-throughput, latency-sensitive paths
• Use JSON for human-readable messages and broad ecosystem compatibility
• Consider backward and forward compatibility when evolving message schemas

WAF Pillar Alignment

Security

Common Mistakes

• Using an inefficient encoding format for high-volume message streams
• Not validating message schemas, allowing malformed data into the processing pipeline

11. Monitoring and Diagnostics

Track system health, usage, and performance through a comprehensive monitoring pipeline that turns raw data into alerts, reports, and automated triggers.

Key Recommendations

• Instrument applications with structured logging, metrics, and distributed tracing
• Use Azure Monitor, Application Insights, and Log Analytics as the monitoring backbone
• Define actionable alerts with clear thresholds, severity levels, and response procedures
• Detect and correct issues before they affect users by monitoring leading indicators
• Correlate telemetry across services using distributed trace context (e.g., correlation IDs)
• Establish performance baselines and track deviations over time
• Build dashboards for operational visibility across all tiers of the architecture
• Review and tune alert rules regularly to reduce noise

WAF Pillar Alignment

Operational Excellence

Common Mistakes

• Insufficient logging, making incident root-cause analysis slow or impossible
• Not using distributed tracing in microservice or multi-tier architectures
• Alert fatigue from poorly tuned thresholds that generate excessive false positives

12. Transient Fault Handling

Detect and handle transient faults caused by momentary loss of network connectivity, temporary service unavailability, or resource throttling.

Key Recommendations

• Implement retry logic with exponential backoff and jitter for transient failures
• Use a circuit breaker pattern to stop retrying when failures are persistent
• Distinguish transient faults (e.g., HTTP 429, 503) from permanent errors (e.g., 400, 404)
• Leverage built-in retry policies in Azure SDKs before adding custom retry logic
• Avoid duplicating retry layers across middleware and application code
• Log every retry attempt for post-incident analysis
• Set a maximum retry count and total timeout to bound retry duration

WAF Pillar Alignment

Reliability

Common Mistakes

• Retrying non-transient faults (e.g., authentication failures, bad requests)
• Not using exponential backoff, overwhelming a recovering service with constant retries
• Retry storms caused by multiple layers retrying simultaneously without coordination

Source: Azure Architecture Center