When it comes to selecting between a serverless Lambda architecture or a standard EC2 virtual machine, several factors should guide your decision, depending on your application requirements, scalability needs, and operational preferences.
Architecture Complexity and Management:
Lambda: AWS Lambda is part of a broader serverless architecture that abstracts the underlying infrastructure management. This means you don’t need to manage or provision servers, allowing for a focus on code and application logic rather than server management. It’s ideal for microservices or event-driven architecture where you want to eliminate maintenance overhead.
EC2 VM: With EC2, you’re responsible for provisioning capacity, managing the server, scaling, and maintaining the EC2 instance. It offers more control over the operating system, installed software, and even better customization possibilities for applications that require specific configurations.
Scalability:
Lambda: Serverless functions scale automatically, handling spikes in traffic seamlessly by invoking multiple instances of your Lambda function. Billing is based only on the compute time consumed rather than the uptime, making it cost-efficient for intermittent workload spikes.
EC2 VM: You need to implement an autoscaling group to manage horizontal scaling, which can be more complex and requires configuration to handle variable workloads. While this provides the potential for scaling, it requires more intervention.
Cost:
Lambda: The pay-as-you-go pricing model can result in significant cost savings for applications with uneven demand, as you pay only for the actual computing time used. Ideal for infrequent tasks or when resource usage is not predictable.
EC2 VM: Typically, you pay for the time an instance is running, and costs can accumulate even if the server is not fully utilized. Suitable for applications with predictable workloads or where continuous 24/7 operation is necessary.
Performance:
Lambda: While it provides rapid scalability, there might be cold-start latency associated with functions that aren’t used frequently. It’s optimized for short-lived tasks and may not be suitable for high-performance applications requiring low-latency responses.
EC2: Offers the full resources of a virtual machine, potentially providing more consistent performance for compute-intensive applications. There is no cold-start time, ensuring immediate response capabilities for long-running processes.
Development and Maintenance:
Lambda: Encourages modern development practices such as function-as-a-service (FaaS), ideally used in conjunction with other AWS services as part of a cloud-native ecosystem. Requires understanding of event-driven programming.
EC2: Suitable for traditional software development, particularly when working with existing applications needing migration or when specific server environments are required.

In conclusion, if your goal is to minimize server management effort, enhance scalability for variable workloads, and potentially reduce costs for low-utilization applications, AWS Lambda is an excellent choice. Conversely, if you require complete control over the server environment, predictable performance, and are running applications with constant uptime or specific configuration needs, using EC2 instances may be more appropriate. Consider your application’s architecture, workload patterns, and operational expertise when making your decision.