In the vast land of Azure integration, one question haunts even the bravest architects: should I use Azure Functions or Logic Apps? While both services are serverless and event-driven, their use cases, capabilities, and underlying execution models differ significantly. Azure Logic Apps are designed for orchestrating workflows with out-of-the-box connectors and a low-code UI, while Azure Functions provide code-level control for building custom logic and lightweight APIs. The choice between them isn’t always clear-cut. It often depends on factors like complexity, throughput, latency, development control, and operational overhead. In this post, we’ll take a scalpel to both services, dissect their differences, and help you choose the right tool for your integration workload — not based on vibes, but based on hard architectural trade-offs.

Let’s start by comparing the execution models. Logic Apps are declarative and stateful by default (though stateless is an option in Standard), making them ideal for long-running workflows and external system orchestration. On the flip side, Azure Functions are imperative and stateless by nature, unless you use Durable Functions to persist state. Functions run as event-triggered code — whether HTTP, timers, queues, or Event Grid — and are ideal for fine-grained logic that doesn’t need orchestration. For example, validating a payload, transforming JSON, or making lightweight external API calls is perfect for Functions. But if you need to call five APIs in sequence with retries, conditional logic, and different authentication mechanisms, Logic Apps might be your better bet. Another factor is connectors: Logic Apps have native, managed connectors (e.g., Salesforce, SAP, SharePoint), while Functions typically rely on SDKs or manual HTTP calls, which increases complexity.

Now let’s talk performance and scalability. Azure Functions shine when you need high throughput with low latency. They scale out automatically and fast, especially with Premium or Elastic Premium plans, and are well-suited for real-time processing workloads. Logic Apps, though scalable, can introduce latency due to the underlying workflow engine and managed connectors. For example, cold starts are more noticeable in Logic Apps Standard unless pre-warmed. Also, Logic Apps have more verbose execution logs due to every action being tracked, which can slightly slow execution — but also gives you detailed insight. In terms of throughput, Functions often win unless you’re leveraging batch processing connectors in Logic Apps like Service Bus with "peek-lock" mode. If you’re building an API backend or a reactive event handler, Azure Functions will likely give you the performance edge. But beware of long-running executions — Azure Functions have a timeout unless explicitly configured with Durable Functions.

Developer experience is another area of divergence. Azure Functions are code-first, integrated with modern CI/CD pipelines, and support languages like C#, Python, JavaScript, and Java. This makes them great for dev teams with strong coding backgrounds. Logic Apps, however, appeal to integration specialists or teams preferring a low-code/no-code experience, especially in business-driven scenarios. With Logic Apps Standard, you can also develop workflows using Visual Studio Code and deploy them like regular code — but you’re still configuring rather than coding. Functions are more flexible, but they demand stricter version control, testing frameworks, and observability tools like Application Insights. Logic Apps provide built-in run history, error tracking, and visual debugging. TL;DR: Logic Apps are easy to pick up, Functions are easier to fine-tune. Choose based on your team's comfort zone and how much control you want over the logic.

From a cost and operations perspective, both services offer consumption-based pricing, but they behave differently. Logic Apps charge per action and connector execution, so a single HTTP call plus a condition check and a loop could rack up costs quickly at scale. Azure Functions charge per execution time and memory, making them more predictable for short-running tasks. However, durable functions (with orchestration and timers) can also add storage and compute overhead. Monitoring costs differ too — Logic Apps integrate easily with Azure Monitor, and every run is stored. Azure Functions require more custom telemetry to get equivalent visibility. On the operations side, Logic Apps tend to be easier to monitor visually, while Functions require more observability tools and alerts. In high-scale environments, operations teams often prefer Functions due to better control of logs, retries, and cold starts. But Logic Apps win in scenarios where business teams need visibility into workflow outcomes without diving into code or Kusto queries.

Ultimately, the best integrations often use both. A Logic App might orchestrate a workflow that invokes Azure Functions for custom business logic or data transformation. Use Logic Apps where you need connectors, orchestration, and clarity; use Functions where you need speed, control, and compact logic. Don’t fall into the trap of picking one just because it’s cooler or more familiar — architecture should serve the use case, not ego. Hybrid models that combine the strengths of both services are increasingly common in mature Azure solutions. Keep latency, scalability, and maintainability top of mind. As a general rule: if your flow looks like a process map, use Logic Apps. If it looks like an algorithm, use Functions. Stay tuned for the next blog, where we’ll walk through a real-world event-driven integration pattern using Logic Apps, Event Grid, and Azure Functions working together in glorious harmony.