16 - Serverless Overviews

Lambda SnapStart

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Overview

Lambda SnapStart improves function performance up to 10x for Java (11+), Python (3.12+) and .NET (8+). It is at no extra cost for Java only; Python and .NET are charged for snapshot caching and restores. It targets slow function initialization (cold starts). Compare with provisioned concurrency.

AWS update (2024-11)

SnapStart is free only for Java. Python (3.12+) and .NET (8+) are charged for snapshot caching and restores. It is not supported with provisioned concurrency, EFS, or ephemeral storage over 512 MB. The course said no extra cost for all three; the exam may still use the course figure. AWS source

Without SnapStart

An invocation goes through three lifecycle phases:

  1. Initialize: the function and its environment are initialized. This can take a long time, for example for a Java function.
  2. Invoke.
  3. Shutdown.

With SnapStart

  1. When you publish a new version of the function, Lambda automatically initializes it.
  2. Lambda takes a snapshot of the memory and disk state.
  3. Invocations use the snapshot for low latency and go directly to the invoke stage, then shutdown.
SnapStart disabled SnapStart enabled
Initialization At invocation time Pre-initialized at version publish
Path Initialize -> Invoke -> Shutdown Snapshot -> Invoke -> Shutdown
Exam Pattern

Faster Lambda startup for Java, Python or .NET -> SnapStart (free for Java; Python and .NET pay for snapshot caching and restores).

AWS update (2024-11)

Only Java SnapStart is free; Python and .NET are charged. AWS source

Questions & Answers

Q1: What does SnapStart do?

Answer:

Pre-initializes the function when a version is published and snapshots memory and disk state, so invocations skip the initialize phase.

Q2: Which runtimes and what cost?

Answer:

Java 11+, Python 3.12+, .NET 8+. No extra cost for Java only; Python and .NET are charged for snapshot caching and restores. Up to 10x better performance.

AWS update (2024-11)

The course said no extra cost for all runtimes. Python and .NET are charged for snapshot caching and restores. AWS source

Check yourself

Quiz

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