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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