How to do Low Level Design for Given HLD in Azure

Question

I have created a High level design where I am consuming JSON file from Azure Stream Analytics to Azure SQL.

What all are properties I should consider for creating Low Level Design for same.

Please help me with your expertise knowledge.

Thanks a lot

Answer 1

Hi there,

Here are some low level consideration for your stream analytics architecture:

Low Level Design: Azure Stream Analytics to SQL Integration

  1. Data Source & Input Configuration

  - Input Type: JSON data from Azure Stream Analytics

  - Serialization Format: JSON (configure compression if needed)

  - Partition Key: Identify a field in your JSON for partition optimization

  - Timestamp Policy: Choose between arrival time or event time (application timestamp)

  - Backfill Option: Configure if historical data processing is needed

  - Input Validation: Enable to verify schema compliance and improve resiliency

  2. JSON Schema Definition

  - Schema Inference: Decide between automatic or explicit schema definition

  - CREATE TABLE: Define explicit schema for reliable processing using ASA's CREATE TABLE

  - Data Types: Map JSON types to appropriate SQL types (string → nvarchar, numeric → decimal/int)

  - Complex Types: Handle nested objects and arrays with proper extraction functions

  - Default Values: Set default values for missing fields if needed

  3. Stream Analytics Query Design

  - Query Optimization: Structure query for efficient processing

  - Temporal Windows: Define tumbling/sliding/hopping windows if aggregation is needed

  - Functions: Implement UDFs for complex transformations if required

  - Error Handling: Use TRY_CAST functions to prevent job failures

  - Partition Hints: Leverage PARTITION BY for parallelism

  - Reference Data: Include reference data joins if required for enrichment

  4. SQL Database Output Configuration

  - Table Design:

    - Primary Key constraints

    - Clustered/Non-clustered indexes on frequently queried columns

    - Appropriate column data types matching ASA output

    - Partitioning scheme if high volume

    - Compression settings for large tables

  - Batch Settings:

    - Max batch count (recommended: 10,000 for optimal performance)

    - Batch size (recommended: 1-2 MB)

  - Authentication: Use Managed Identity for secure connection

  - Retry Policy: Configure appropriate retry settings

  - Column Mapping: Define explicit column mapping if field names differ

  5. Performance Optimization

  - Streaming Units (SUs): Allocate appropriate SUs (start with at least 6 SUs for production)

  - Partitioning Strategy:

    - Enable "Inherit Partitioning" option for parallelism

    - Ensure balanced partitioning to avoid hotspots

  - SQL Database Tier: Select appropriate service tier (Premium/Business Critical for high throughput)

  - SQL Indexing Strategy: Implement proper indices on frequently queried columns

  - Compatibility Level: Use latest ASA compatibility level for best performance

  - Watermark Delay: Monitor and optimize to maintain processing speed

  6. Monitoring & Alerting

  - Key Metrics to Monitor:

    - Watermark delay (target <10 seconds for real-time processing)

    - SU utilization (target <80%)

    - Input/Output events rate

    - Runtime errors

    - Failed function calls

    - Resource utilization

  - Alert Thresholds:

    - Watermark delay > 1 minute

    - SU utilization > 80% for 15+ minutes

    - Runtime errors > 0

    - Input events with deserialization errors

  - Logging Configuration:

    - Enable diagnostic logs

    - Set up Log Analytics workspace

    - Configure proper retention period

  7. Error Handling & Data Quality

  - Input Data Validation: Implement schema validation at input

  - Dead-letter Path: Configure for invalid/unprocessable events

  - Error Handling Strategy:

    - DROP errors: Discard invalid records

    - RETRY: For transient failures

    - Exception path for detailed troubleshooting

  - Data Quality Checks:

    - Implement checksum validation if applicable

    - Set up data quality monitoring dashboards

  8. Security & Compliance

  - Data Encryption: Enable encryption at rest and in transit

  - Secure Authentication:

    - Use Azure Active Directory (AAD) and Managed Identity

    - Avoid shared credentials/connection strings

  - Network Security:

    - Implement Private Endpoints or Service Endpoints

    - Configure firewall rules appropriately

  - Auditing: Enable SQL auditing for compliance requirements

  - Access Control: Implement proper RBAC for both ASA and SQL

  9. Disaster Recovery & Business Continuity

  - Geo-replication: Set up SQL geo-replication if needed

  - Backup Strategy: Configure SQL automated backups

  - Job Recovery Plan: Document steps for job recovery

  - Configuration Versioning: Store job definitions in source control

  - Failover Testing: Regularly test failover scenarios

  10. Deployment & DevOps

  - CI/CD Pipeline: Implement automated deployment

  - Environment Promotion: Dev → Test → Prod strategy

  - ARM Templates/Bicep: Infrastructure as code for reproducibility

  - Feature Flags: For controlled rollout of changes

  - Blue-Green Deployment: For zero-downtime updates

  11. Cost Optimization

  - Right-sizing: Adjust SUs based on actual load patterns

  - SQL Resource Optimization: Implement elastic pools if applicable

  - Data Lifecycle Management: Configure data retention/archiving

  - Scheduled Scaling: Implement scheduled scaling for predictable workloads

  - Cost Monitoring: Set up cost alerts and regular reviews

  12. Documentation & Governance

  - Data Dictionary: Document all fields and their mappings

  - SLA Definitions: Define performance and availability SLAs

  - Runbook: Create operational procedures for common issues

  - Change Management: Establish change control processes

  - Knowledge Transfer: Ensure team training on the solution

References:

https://learn.microsoft.com/en-us/azure/stream-analytics/

https://learn.microsoft.com/en-us/stream-analytics-query/stream-analytics-query-language-reference