What Was Announced
March 2026 brought two significant AWS developer updates affecting runtime support and SDK lifecycle. On the positive side, AWS Lambda Managed Instances added Rust to its supported runtime list. On the deprecation front, the AWS SDK for .NET v3 and AWS Tools for PowerShell v4 both entered maintenance mode on March 1, 2026, with a hard end-of-support date of June 1, 2026.
Key Features and Changes
AWS Lambda Managed Instances: Rust Support
AWS Lambda Managed Instances is the execution model that allows Lambda functions to run in long-lived, pre-warmed instances — reducing cold start impact significantly for latency-sensitive workloads. Rust is now a supported runtime for Managed Instances, joining Java, Python, Node.js, and Go.
Rust's combination of near-zero runtime overhead, deterministic memory usage (no GC pauses), and memory safety makes it a compelling option for Lambda functions that need consistent sub-millisecond execution. With Managed Instances, the Rust binary is loaded into a warm instance and reused across invocations, eliminating the cold start penalty that previously made Rust less attractive than JVM-warmed runtimes for high-frequency functions.
AWS SDK for .NET v3 — End-of-Support June 1, 2026
The AWS SDK for .NET v3 entered maintenance mode on March 1 and will reach full end-of-support on June 1, 2026. After that date, the SDK will receive no further bug fixes, security patches, or feature updates. Teams still on v3 should migrate to v4 before the deadline.
Key improvements in v4:
- Async-first APIs — All service operations are async by default; synchronous wrappers are removed
- Source-generated serialization — Faster JSON marshalling using .NET source generators, reducing startup time and memory allocation
- Improved performance — Benchmarks show 20–40% throughput improvements for common operations
- Cleaner credential chain — Simplified credential resolution order and better support for container/EC2 credential providers
AWS Tools for PowerShell v4 — Same Timeline
PowerShell v4 also entered maintenance mode on March 1 with the same June 1 EOL. Teams using PowerShell for AWS automation should migrate to v5, which includes better tab-completion, improved pipeline support, and PowerShell 7 compatibility.
Amazon Bedrock AgentCore GA
AWS also announced GA of Amazon Bedrock AgentCore with new stateful runtime improvements. This includes memory streaming notifications for long-running agents, allowing agents to maintain context across multiple sessions without manual state management.
Why It Matters for Developers
The .NET SDK v3 EOL is the most time-sensitive item here — June 1 is three months away. For .NET teams running production workloads on AWS, this is a real migration deadline, not a soft recommendation. The v4 migration is generally straightforward but involves updating API call patterns from synchronous to async, which can cascade through a codebase if .GetAwaiter().GetResult() patterns were used to work around async in older code.
The Rust Lambda support is a welcome addition for performance-critical functions, and the Managed Instances model removes the traditional cold-start objection to using Rust on Lambda.
Source
Read the original article — AWS Developer Blog
