AWS Lambda Managed Instances

AWS Lambda Managed Instances (LMI)

Run Lambda functions on current-generation EC2 instances in your account while AWS manages provisioning, patching, scaling, routing, and load balancing. Combines Lambda's developer experience with EC2's pricing and hardware options.

For standard Lambda development, see aws-lambda skill. For SAM/CDK deployment, see aws-serverless-deployment skill.

When to Load Reference Files

• Cost comparison, pricing analysis, Lambda vs LMI cost, Savings Plans, or Reserved Instances -> see references/cost-comparison.md
• Instance types, memory sizing, vCPU ratios, scaling tuning, scheduled scaling, or capacity provider config -> see references/configuration-guide.md
• Thread safety, concurrency model, code review checklist, Powertools compatibility, or multi-concurrency readiness -> see references/thread-safety.md
• Before/after code examples, runtime-specific migration (Node.js, Python, Java, .NET), or connection pooling -> see references/migration-patterns.md
• IAM roles, VPC setup, CLI commands, SAM template, CDK example, or scheduled scaling setup (EventBridge Scheduler) -> see references/infrastructure-setup.md and scripts/setup-lmi.sh
• Errors, throttling, debugging, stuck deployments, tuning configuration, or adjusting after deployment -> see references/troubleshooting.md

Quick Decision: Is LMI Right for This Workload?

Instructions

Step 1: Assess the Workload

Gather these signals before recommending:

1. Traffic pattern: Steady vs bursty? Requests per second?
2. Current costs: Monthly Lambda spend? Existing Savings Plans?
3. Runtime: Node.js, Java, .NET, or Python?
4. Memory/CPU: How much memory? CPU-bound or I/O-bound?
5. Execution duration: Average and P99?
6. Concurrency readiness: Thread safety (Node.js/Java/.NET)? Shared /tmp paths? Per-invocation DB connections?
7. VPC: Already in a VPC? Private resource access needed?

Deriving LMI Configuration from Metrics

If Lambda Insights is enabled on the function, use these metrics to calculate your starting configuration. If Lambda Insights is not enabled, suggest adding it to gather accurate workload data — but only proceed with the user's explicit confirmation, as adding the Insights layer may affect function performance or cold start times.

To check if Lambda Insights is enabled, look for a LambdaInsightsExtension layer on the function. To add it, find the latest layer ARN for your region from the Lambda Insights documentation and attach the CloudWatchLambdaInsightsExecutionRolePolicy managed policy to the function's execution role.

Target max concurrency (from cpu_total_time and Duration):

PerExecutionEnvironmentMaxConcurrency = floor((0.5 × Duration) / cpu_total_time)

This targets 50% CPU utilization at full concurrency, leaving headroom for scaling.

Memory allocation (from memory_utilization and current memory):

MemorySize = min(32768, max(2048, MaxConcurrency × (memory_utilization / 100) × current_allocated_memory))

This overestimates (assumes no shared base memory) but provides a safe starting point. The outer min caps the result at the 32 GB (32768 MB) LMI maximum.

Minimum execution environments (from baseline ConcurrentExecutions):

MinExecutionEnvironments = max(3, ceil(baseline_concurrent_executions × 2 / MaxConcurrency))

Targets 50% concurrency utilization to leave headroom for traffic bursts.

Without Lambda Insights: Start with the runtime's default max concurrency, 2 GB memory, and MinExecutionEnvironments = 3. Adjust during testing.

Step 2: Build the Cost Comparison

REQUIRED: Present a cost comparison before recommending LMI. Compare at minimum:

Rule of thumb: LMI becomes cost-competitive when your Lambda spend exceeds ~$1,000/month with steady traffic.

For discount analysis (Savings Plans, Reserved Instances), refer users to the AWS Pricing Calculator and references/cost-comparison.md for formulas and worked examples. Discount recommendations require workload-specific forecasting beyond this skill's scope.

Step 3: Configure the Deployment

Instance families (~450 types): C-series (compute, .xlarge+), M-series (general, .large+), R-series (memory, .large+). ARM (Graviton) for best price-performance.

Memory-to-vCPU ratios: 2:1 (default, CPU-bound work), 4:1 (general/mixed workloads), 8:1 (memory-heavy or Python apps). Min 2 GB, max 32 GB.

Multi-concurrency defaults/vCPU: Node.js 64, Java 32, .NET 32, Python 16.

Scaling: MinExecutionEnvironments (default 3), MaxVCpuCount (default 400), TargetResourceUtilization.

Scheduled scaling: For predictable traffic (business hours, marketing events), use EventBridge Scheduler to adjust Min/Max execution environments on a one-time or recurring schedule — scale up before peak, scale down or to zero when idle.

See references/configuration-guide.md for decision trees and detailed tuning.

Step 4: Migrate the Code

Review code for concurrency safety. LMI runs multiple invocations concurrently per execution environment, but the model differs by runtime:

• Python: Process-based isolation — globals are NOT shared. No thread-safety changes needed. Focus on /tmp conflicts and memory sizing (per-process × concurrency).
• Node.js: Worker threads — globals shared within a worker. Requires async safety. Callback handlers not supported on Node.js 22.
• Java/.NET: OS threads/Tasks — handler shared across threads. Requires full thread safety.

Common issues (all runtimes): shared /tmp paths, per-invocation DB connections. Thread-safety issues (Node.js/Java/.NET only): mutable globals, non-thread-safe libs.

See references/thread-safety.md for the review checklist and references/migration-patterns.md for runtime-specific before/after code.

Step 5: Set Up Infrastructure

1. Create two IAM roles: execution role (for the function) and operator role (for capacity provider EC2 management)
2. Configure VPC with subnets across multiple AZs (recommended 3+ for resiliency)
3. Create capacity provider with VPC config and scaling limits
4. Create or update function with capacity provider attachment
5. Publish a version (triggers instance provisioning)

See references/infrastructure-setup.md for CLI commands and SAM templates.