Guide on Azure Serverless Computing: Functions

June 16, 2022

Prabhu Perumal Renita Joan


Guide on Azure Serverless Computing: Functions

Azure Functions is a serverless computing solution that allows organizations to run code on-demand without managing infrastructure or hosting it on a server. It helps to easily run the small pieces of code or functions in the cloud. Developers can concentrate on writing the function to solve the business problem without worrying about the infrastructure.

Some of the major benefits of serverless computing that need to be considered:

  • Serverless coding platform (Function as a Service-FaaS)
  • Specifically designed for nano-service and event-based applications
  • Supports multiple languages – .NET, Core Java, JavaScript (NodeJS), Python, PowerShell & TypeScript
  • Price is super cheap as it is a pay-per-use model
  • Developers can use their dependencies through NPM or NuGet
  • Highly secure as it is integrated into Azure active directory
  • Flexible development – Develop in Azure portal or visual studio code or any other IDEs
  • Integration with Github, Azure DevOps, etc. for automated deployments
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Function app flow

Components of a function app:


To execute the piece of code, we need something called a trigger. A trigger defines when the function should be executed, and the associated data is often provided as input for the function. A function must have exactly one trigger.


Bindings are a way to connect another resource to the function – it can be connected as input bindings, output bindings, or both. Binding data is provided as input for the function to execute code or the processed output sent to an output binding. 

Example scenarios on how to implement different functions: 

Trigger Scenario Input Binding Output binding 
HTTP Persist the data payload sent over HTTP into Azure SQL database None Azure SQL 
CosmosDB Trigger Persist the Cosmos document changes into Azure SQL transactional database None Azure SQL 
BlobTrigger Whenever a new blob is created process the file and move it to an archive location Blob Storage Blob Storage 
Timer A scheduled job reads data from Azure SQL and sends out a report email Azure SQL None 


Supported Bindings: 

Here are some of the bindings supported by Azure functions runtime version 2.X 

Trigger Type Trigger Input Output 
Blob Storage Yes Yes Yes 
Cosmos DB Yes Yes Yes 
Azure SQL  Yes Yes 
Event Grid Yes  Yes 
HTTP Yes  Yes 
Service Bus Yes  Yes 
Timer Yes   
Twilio   Yes 


Hosting plans 

The hosting plan influences the function executions’ performance, reliability, and cost. The following hosting plans are available for Function apps: 

 Consumption plan 

  • Fully serverless hosting option 
  • Scales automatically based on the events 
  • Function execution times out after a configurable time 
  • Billing based on number of executions, execution time, and memory used 

 Premium plan 

  • Premium plans scale dynamically based on the number of events 
  • Avoid cold starts with perpetually warm instances 
  • Virtual network connectivity 
  • Unlimited execution duration, with 60 minutes guaranteed 
  • Premium instance sizes 
  • More predictable pricing 

 Dedicated (App service) plan 

  • Run Functions at regular App Service plan rates 
  • Good fit for long running operations 
  • Good fit for predictive scaling and costs  

Best Practices 

The best practices to follow when writing function code that helps with the performance and availability of your functions; 

  1. Avoid long-running functions that cause timeout issues 
  2. Write functions to be stateless 
  3. Write defensive functions 
  4. Follow retry patterns 
  5. Avoid a lot of dependencies as it will cause cold start problems  

Function app limitations 

Resource Consumption plan Premium plan App service plan 
Max instances 200 20 10-20 
Timeout duration (Min) Default=5, Max=10 Default=30, Max=Unlimited Default=900, Max=Unlimited 
Max request size (MB) 100 100 100 
Azure compute unit per instance 100 210-840 100-840 
Function apps per plan 100 100 Unlimited 
Storage 1GB 250GB 500-1000GB 
Custom domains per app 500 500 500 


Consumption plan 

Meter Price Free Grant (per month) 
Execution Time $0.000016/GB-s 400000 GB-s 
Total Executions $0.20 per million executions 1 million executions 

 Premium plan 

Meter Price 
vCPU duration $0.173 vCPU/hour 
Memory duration $0.0123 GB/hour 
A trigger-based service, Azure Functions, ensures running a script or piece of code in response to various situations. It can be used to achieve decoupling, high throughput and reusability.  To know more about serverless computing and the services Azure offer, follow our series on the Guide to Azure serverless computing options and also get an in-depth understanding from our cloud experts here! 

Disclaimer: All the images used in this series of blogs are sourced from the official Microsoft™ Azure Serverless computing charts and pictography. 

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