Best practices for beginners in Azure Functions?

For beginners with Azure Functions, focus on three areas: how functions are organized, how they are developed and tested locally, and how to avoid common reliability/performance issues.

1. Structuring functions for maintainability

• Organize by responsibility and privilege:
  • Group related functions into the same Function App when they share configuration and lifecycle.
  • If some functions need different configuration (for example, different connection strings or credentials), move them into a separate Function App so host.json and app settings can be tuned per group.
  • Organize functions by privilege: any connection string or credential in app settings is shared by all functions in that Function App. Minimize the number of functions that have access to sensitive credentials by placing unrelated functions in a different Function App. Use techniques such as function chaining between apps when needed.
• Keep functions small and focused:
  • Avoid large, long-running functions. Refactor into smaller functions that work together.
  • For HTTP/webhook scenarios, return quickly and offload heavy work to background triggers (for example, put a message on a queue and process it with a queue-triggered function).
• Use host.json carefully:
  • host.json applies to all functions in the Function App. If only some functions need custom trigger/runtime behavior, consider a separate Function App instead of overloading host.json with conflicting settings.

2. Local testing and debugging

• Use supported local environments:
  • Visual Studio, Visual Studio Code (with the Azure Functions extension), or command line with Azure Functions Core Tools are all supported for local development and debugging. All rely on Core Tools to run the real Functions runtime locally.
• Use a local storage emulator when applicable:
  • For functions that use Azure Storage bindings (Queue, Blob, Table), configure local.settings.json with:

        "AzureWebJobsStorage": "UseDevelopmentStorage=true"
    

    This tells the local Functions host to use the Azurite emulator instead of a real storage account.
  • Ensure Azurite is installed and running.
  • Before publishing, test at least once against a real Azure Storage account.
  • Never publish a Function App with AzureWebJobsStorage set to UseDevelopmentStorage=true; in Azure this setting must be a real storage connection string.

3. Common pitfalls and how to avoid them

• Long-running or blocking functions:
  • Long-running functions can hit timeout limits depending on the hosting plan. Design functions to complete quickly and offload long work to background triggers or use Durable Functions for orchestrating long-running workflows.
• Untracked background work:
  • Any tasks, threads, or processes started by a function must complete before the function returns. The runtime does not track background threads; if the site shuts down, they can be terminated mid-work. Always await asynchronous work and avoid fire-and-forget patterns for essential logic.
• Node.js-specific patterns (if using Node.js):
  • Prefer single-vCPU App Service plans for Node.js Functions; they are more efficient for this runtime and scale out by adding instances.
  • Run from a package file to reduce cold start time, especially when there are many dependencies.
  • Use a single static client for external services (for example, storage, databases) in global scope to avoid connection limits.
  • Use async/await instead of callbacks or .then/.catch to avoid uncaught exceptions and missing logs.
• Missing observability:
  • Enable monitoring with Application Insights and Azure Monitor to track health, performance, and failures.
  • Configure alerts on critical metrics and use dashboards for visibility.
• No automated deployment path:
  • Use CI/CD pipelines (Azure DevOps or GitHub Actions) to automate deployments for consistency and safer releases.
  • Use deployment slots for staging and safe rollouts when appropriate.
• Reliability and scaling:
  • Configure automatic retries for transient errors using built-in retry policies.
  • Use Durable Functions for complex or long-running workflows that need state and reliability.
  • Rely on automatic scale-out based on the hosting plan and trigger type; design functions to be stateless and idempotent where possible.

These practices help keep Azure Functions apps maintainable, testable, and reliable as they grow beyond initial experiments.

References:

• Improve the performance and reliability of Azure Functions
• Architecture best practices for Azure Functions
• Azure Functions Node.js developer guide (nodejs-model-v3)
• Code and test Azure Functions locally (programming-language-typescript)
• Code and test Azure Functions locally (programming-language-csharp)