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Tips and Tricks

Always set functions' memory, timeout, and log retention.​

Otherwise, you will get defaults, which may not be best for your specific case.

Limited log retention will save you costs for storing old Lambda logs that you won't look at anyway

provider:
  # common for all functions
  memorySize: 512
  timeout: 10
  logRetentionInDays: 14 ## allowed values: 1, 3, 5, 7, 14, 30, 60, 90, 120, 150, 180, 365, ....

functions:
  firstFunction:
    handler: index.handler
    # function-specific
    memorySize: 512

enable HTTP keep-alive​

Read here on what this means.

environment:
  AWS_NODEJS_CONNECTION_REUSE_ENABLED: 1

Package functions individually​

Package functions into separate bundles to reduce their size and Lambda cold start.

functions:
  firstFunction:
    handler: index.firstHandler
  secondFunction:
    handler: index.secondHandler
  email:

package:
  individually: true

Here are useful resources for cold starts, tuning lambdas, and faster functions

Don't import whole SDKs when not needed to reduce function size​

Do not import the whole AWS SDK like so:

import {CloudFront, Lambda} from 'aws-sdk'

Instead, do it like this:

import CloudFront from 'aws-sdk/clients/cloudfront'
import Lambda from 'aws-sdk/clients/lambda'

Override generated resource parameters if needed.​

Core Serverless Framework (SF) and various plugins reduce boilerplate by generating some resources for us. It's no magic, just CloudFormation resources.

For example, until SF supported IAM auth for HTTP API, we could configure it by ourselves.

functions:
  firstFunction:
    handler: index.firstHandler
    events:
      -httpApi:
        path: /
        method: GET

resources:
  extensions:
    HttpApiRouteGet:
      Properties:
        AuthorizationType: AWS_IAM

Set variable values depending on the stage.​

You can use a config directory with the structure:

app
├── config
│   └── config.dev.json
│   └── config.staging.json
│   └── config.production.json
└── serverless.yml
custom:
  bucketName: ${file(config/config.${self:custom.currentStage}.json):BUCKET_NAME}

provider:
  environment:
    LOG_LEVEL: ${file(config/config.${self:custom.currentStage}.json):LOG_LEVEL}

Provider/function level variables​

Set common environment variables at the provider level, and function-specific variables at the function level. They will be merged together and all will be available in the Lambda runtime.

environment variables

Re-use deployment bucket​

If having a project consisting of multiple stacks, reuse a single deployment bucket to limit the number of S3 buckets (and how often you need to request buckets number quota increased).

provider:
  deploymentBucket:
    name: com.serverless.${self:app}.${self:provider.region}.${self:custom.currentStage}.deploys

Disable Lambda versioning​

If not using Lambda versions for rollback etc., disable them. Otherwise, use a plugin to keep only X latest versions.

This will reduce used storage, as it's easier to hit the (default) 75 GB Lambda total size quota than you think.

provider:
  versionFunctions: false

Use CloudFormation resource names​

Let CloudFormation generate resource names for you. In most cases, it will start with the stack name, with a random suffix.

It will result in consistent, easily identifiable, and unique names. And sometimes not specifying the name blocks some CF updates.

cloudformation resource names