Parameters

The Parameters utility provides high-level functions to retrieve one or multiple parameter values from AWS Systems Manager Parameter Store, AWS Secrets Manager, AWS AppConfig, Amazon DynamoDB, or your own parameter store.

Key features

• Retrieve one or multiple parameters from the underlying provider
• Cache parameter values for a given amount of time (defaults to 5 seconds)
• Transform parameter values from JSON or base64 encoded strings
• Bring Your Own Parameter Store Provider

Getting started

The Parameters Utility helps to retrieve parameters from the System Manager Parameter Store (SSM), secrets from the Secrets Manager, and application configuration from AppConfig. Additionally, the utility also offers support for a DynamoDB provider, enabling the retrieval of arbitrary parameters from specified tables.

Installation

Note

This utility supports AWS SDK for JavaScript v3 only. This allows the utility to be modular, and you to install only the SDK packages you need and keep your bundle size small.

Depending on the provider you want to use, install the library and the corresponding AWS SDK package:

SSMProviderSecretsProviderAppConfigProviderDynamoDBProvider

npminstall@aws-lambda-powertools/parameters@aws-sdk/client-ssm 

npminstall@aws-lambda-powertools/parameters@aws-sdk/client-secrets-manager 

npminstall@aws-lambda-powertools/parameters@aws-sdk/client-appconfigdata 

npminstall@aws-lambda-powertools/parameters@aws-sdk/client-dynamodb@aws-sdk/util-dynamodb 

Tip

If you are using the nodejs18.x runtime or newer, the AWS SDK for JavaScript v3 is already installed and you can install the utility only.

IAM Permissions

This utility requires additional permissions to work as expected.

Note

Different parameter providers require different permissions.

Provider	Function/Method	IAM Permission
SSM	getParameter, SSMProvider.get	ssm:GetParameter
SSM	getParameters, SSMProvider.getMultiple	ssm:GetParametersByPath
SSM	getParametersByName, SSMProvider.getParametersByName	ssm:GetParameter and ssm:GetParameters
SSM	If using decrypt: true	You must add an additional permission kms:Decrypt
SSM	setParameter, SSMProvider.set	ssm:PutParameter
Secrets	getSecret, SecretsProvider.get	secretsmanager:GetSecretValue
DynamoDB	DynamoDBProvider.get	dynamodb:GetItem
DynamoDB	DynamoDBProvider.getMultiple	dynamodb:Query
AppConfig	getAppConfig, AppConfigProvider.getAppConfig	appconfig:GetLatestConfiguration and appconfig:StartConfigurationSession

Fetching parameters

You can retrieve a single parameter using the getParameter high-level function.

import{getParameter}from'@aws-lambda-powertools/parameters/ssm';exportconsthandler=async():Promise<void>=>{// Retrieve a single parameterconstparameter=awaitgetParameter('/my/parameter');console.log(parameter);};

For multiple parameters, you can use either:

• getParameters to recursively fetch all parameters by path.
• getParametersByName to fetch distinct parameters by their full name. It also accepts custom caching, transform, decrypt per parameter.

getParametersgetParametersByName

import{getParameters}from'@aws-lambda-powertools/parameters/ssm';exportconsthandler=async():Promise<void>=>{/** * Retrieve multiple parameters from a path prefix recursively. * This returns an object with the parameter name as key */constparameters=awaitgetParameters('/my/path/prefix');for(const[key,value]ofObject.entries(parameters||{})){console.log(`${key}: ${value}`);}};

import{Transform}from'@aws-lambda-powertools/parameters';import{getParametersByName}from'@aws-lambda-powertools/parameters/ssm';importtype{SSMGetParametersByNameOptions}from'@aws-lambda-powertools/parameters/ssm/types';constprops:Record<string,SSMGetParametersByNameOptions>={'/develop/service/commons/telemetry/config':{maxAge:300,transform:Transform.JSON,},'/no_cache_param':{maxAge:0},'/develop/service/payment/api/capture/url':{},// When empty or undefined, it uses default values};exportconsthandler=async():Promise<void>=>{// This returns an object with the parameter name as keyconstparameters=awaitgetParametersByName(props,{maxAge:60});for(const[key,value]ofObject.entries(parameters)){console.log(`${key}: ${value}`);}};

getParametersByName supports graceful error handling

By default, the provider will throw a GetParameterError when any parameter fails to be fetched. You can override it by setting throwOnError: false.

When disabled, instead the provider will take the following actions:

• Add failed parameter name in the _errors key, e.g., { _errors: [ '/param1', '/param2' ] }
• Keep only successful parameter names and their values in the response
• Throw GetParameterError if any of your parameters is named _errors

import{getParametersByName}from'@aws-lambda-powertools/parameters/ssm';importtype{SSMGetParametersByNameOptions}from'@aws-lambda-powertools/parameters/ssm/types';constprops:Record<string,SSMGetParametersByNameOptions>={'/develop/service/commons/telemetry/config':{maxAge:300,transform:'json',},'/this/param/does/not/exist':{},// <- Example of non-existent parameter};exportconsthandler=async():Promise<void>=>{const{_errors:errors,...parameters}=awaitgetParametersByName(props,{throwOnError:false,});// Handle gracefully, since `/this/param/does/not/exist` will only be available in `_errors`if(errors?.length){console.error(`Unable to retrieve parameters: ${errors.join(',')}`);}for(const[key,value]ofObject.entries(parameters)){console.log(`${key}: ${value}`);}};

Storing parameters

You can store parameters in the System Manager Parameter Store using setParameter.

import{setParameter}from'@aws-lambda-powertools/parameters/ssm';exportconsthandler=async():Promise<void>=>{// Store a string parameterconstparameter=awaitsetParameter('/my/parameter',{value:'my-value'});console.log(parameter);};

If the parameter is already existent, it needs to have the overwrite parameter set to true to update the value.

import{setParameter}from'@aws-lambda-powertools/parameters/ssm';exportconsthandler=async():Promise<void>=>{// Overwrite a string parameterconstparameter=awaitsetParameter('/my/parameter',{value:'my-value',overwrite:true,});console.log(parameter);};

Fetching secrets

You can fetch secrets stored in Secrets Manager using getSecret.

import{getSecret}from'@aws-lambda-powertools/parameters/secrets';exportconsthandler=async():Promise<void>=>{// Retrieve a single secretconstsecret=awaitgetSecret('my-secret');console.log(secret);};

Fetching app configurations

You can fetch application configurations in AWS AppConfig using getAppConfig.

The following will retrieve the latest version and store it in the cache.

import{getAppConfig}from'@aws-lambda-powertools/parameters/appconfig';exportconsthandler=async():Promise<void>=>{// Retrieve a configuration, latest versionconstconfig=awaitgetAppConfig('my-configuration',{environment:'my-env',application:'my-app',});console.log(config);};

When using getAppConfig, the underlying provider is cached. To fetch from different applications or environments, create separate AppConfigProvider instances for each application/environment combination.

Advanced

Adjusting cache TTL

By default, the provider will cache parameters retrieved in-memory for 5 seconds.

You can adjust how long values should be kept in cache by using the param maxAge, when using get() or getMultiple() methods across all providers.

Tip

If you want to set the same TTL for all parameters, you can set the POWERTOOLS_PARAMETERS_MAX_AGE environment variable. This will override the default TTL of 5 seconds but can be overridden by the maxAge parameter.

import{SSMProvider}from'@aws-lambda-powertools/parameters/ssm';constparametersProvider=newSSMProvider();exportconsthandler=async():Promise<void>=>{// Retrieve a single parameter and cache it for 1 minuteconstparameter=awaitparametersProvider.get('/my/parameter',{maxAge:60,});// (1)console.log(parameter);// Retrieve multiple parameters from a path prefix and cache them for 2 minutesconstparameters=awaitparametersProvider.getMultiple('/my/path/prefix',{maxAge:120,});for(const[key,value]ofObject.entries(parameters||{})){console.log(`${key}: ${value}`);}};

1. Options passed to get(), getMultiple(), and getParametersByName() will override the values set in POWERTOOLS_PARAMETERS_MAX_AGE environment variable.

Info

The maxAge parameter is also available in high level functions like getParameter, getSecret, etc.

Always fetching the latest

If you'd like to always ensure you fetch the latest parameter from the store regardless if already available in cache, use the forceFetch parameter.

import{getParameter}from'@aws-lambda-powertools/parameters/ssm';exportconsthandler=async():Promise<void>=>{// Retrieve a single parameterconstparameter=awaitgetParameter('/my/parameter',{forceFetch:true});console.log(parameter);};

Built-in provider class

For greater flexibility such as configuring the underlying SDK client used by built-in providers, you can use their respective Provider Classes directly.

Tip

This can be used to retrieve values from other regions, change the retry behavior, etc.

SSMProvider

import{SSMProvider}from'@aws-lambda-powertools/parameters/ssm';importtype{SSMClientConfig}from'@aws-sdk/client-ssm';constclientConfig:SSMClientConfig={region:'us-east-1'};constparametersProvider=newSSMProvider({clientConfig});exportconsthandler=async():Promise<void>=>{// Retrieve a single parameterconstparameter=awaitparametersProvider.get('/my/parameter');console.log(parameter);// Retrieve multiple parameters from a path prefixconstparameters=awaitparametersProvider.getMultiple('/my/path/prefix');for(const[key,value]ofObject.entries(parameters||{})){console.log(`${key}: ${value}`);}};

The AWS Systems Manager Parameter Store provider supports two additional arguments for the get() and getMultiple() methods:

Parameter	Default	Description
decrypt	false	Will automatically decrypt the parameter (see required IAM Permissions).
recursive	true	For getMultiple() only, will fetch all parameter values recursively based on a path prefix.

Tip

If you want to always decrypt parameters, you can set the POWERTOOLS_PARAMETERS_SSM_DECRYPT=true environment variable. This will override the default value of false but can be overridden by the decrypt parameter.

import{SSMProvider}from'@aws-lambda-powertools/parameters/ssm';constparametersProvider=newSSMProvider();exportconsthandler=async():Promise<void>=>{constdecryptedValue=awaitparametersProvider.get('/my/encrypted/parameter',{decrypt:true});// (1)console.log(decryptedValue);constnoRecursiveValues=awaitparametersProvider.getMultiple('/my/path/prefix',{recursive:false});for(const[key,value]ofObject.entries(noRecursiveValues||{})){console.log(`${key}: ${value}`);}};

1. Options passed to get(), getMultiple(), and getParametersByName() will override the values set in POWERTOOLS_PARAMETERS_SSM_DECRYPT environment variable.

SecretsProvider

import{SecretsProvider}from'@aws-lambda-powertools/parameters/secrets';importtype{SecretsManagerClientConfig}from'@aws-sdk/client-secrets-manager';constclientConfig:SecretsManagerClientConfig={region:'us-east-1'};constsecretsProvider=newSecretsProvider({clientConfig});exportconsthandler=async():Promise<void>=>{// Retrieve a single secretconstsecret=awaitsecretsProvider.get('my-secret');console.log(secret);};

AppConfigProvider

The AWS AppConfig provider requires two arguments when initialized:

Parameter	Mandatory in constructor	Alternative	Description
application	No	POWERTOOLS_SERVICE_NAME env variable	The application in which your config resides.
environment	Yes	(N/A)	The environment that corresponds to your current config.

import{AppConfigProvider}from'@aws-lambda-powertools/parameters/appconfig';importtype{AppConfigDataClientConfig}from'@aws-sdk/client-appconfigdata';constclientConfig:AppConfigDataClientConfig={region:'us-east-1'};constconfigsProvider=newAppConfigProvider({application:'my-app',environment:'my-env',clientConfig,});exportconsthandler=async():Promise<void>=>{// Retrieve a configconstconfig=awaitconfigsProvider.get('my-config');console.log(config);};

DynamoDBProvider

The DynamoDB Provider does not have any high-level functions and needs to know the name of the DynamoDB table containing the parameters.

DynamoDB table structure for single parameters

For single parameters, you must use id as the partition key for that table.

Example

DynamoDB table with id partition key and value as attribute

id	value
my-parameter	my-value

With this table, await dynamoDBProvider.get('my-param') will return my-value.

handler.tsDynamoDB Local example

import{DynamoDBProvider}from'@aws-lambda-powertools/parameters/dynamodb';constdynamoDBProvider=newDynamoDBProvider({tableName:'my-table'});exportconsthandler=async():Promise<void>=>{// Retrieve a value from DynamoDBconstvalue=awaitdynamoDBProvider.get('my-parameter');console.log(value);};

You can initialize the DynamoDB provider pointing to DynamoDB Local using the endpoint field in the clientConfig parameter:

import{DynamoDBProvider}from'@aws-lambda-powertools/parameters/dynamodb';constdynamoDBProvider=newDynamoDBProvider({tableName:'my-table',clientConfig:{endpoint:'http://localhost:8000',},});exportconsthandler=async():Promise<void>=>{// Retrieve a value from DynamoDBconstvalue=awaitdynamoDBProvider.get('my-parameter');console.log(value);};

DynamoDB table structure for multiple values parameters

You can retrieve multiple parameters sharing the same id by having a sort key named sk.

Example

DynamoDB table with id primary key, sk as sort key and value as attribute

id	sk	value
my-hash-key	param-a	my-value-a
my-hash-key	param-b	my-value-b
my-hash-key	param-c	my-value-c

With this table, await dynamoDBProvider.getMultiple('my-hash-key') will return a dictionary response in the shape of sk:value.

handler.tsvalues response object

import{DynamoDBProvider}from'@aws-lambda-powertools/parameters/dynamodb';constdynamoDBProvider=newDynamoDBProvider({tableName:'my-table'});exportconsthandler=async():Promise<void>=>{/** * Retrieve multiple values by performing a Query on the DynamoDB table. * This returns a dict with the sort key attribute as dict key. */constvalues=awaitdynamoDBProvider.getMultiple('my-hash-key');for(const[key,value]ofObject.entries(values||{})){// key: param-a// value: my-value-aconsole.log(`${key}: ${value}`);}};

{"param-a":"my-value-a","param-b":"my-value-b","param-c":"my-value-c"}

Customizing DynamoDBProvider

DynamoDB provider can be customized at initialization to match your table structure:

Parameter	Mandatory	Default	Description
tableName	Yes	(N/A)	Name of the DynamoDB table containing the parameter values.
keyAttr	No	id	Hash key for the DynamoDB table.
sortAttr	No	sk	Range key for the DynamoDB table. You don't need to set this if you don't use the getMultiple() method.
valueAttr	No	value	Name of the attribute containing the parameter value.

import{DynamoDBProvider}from'@aws-lambda-powertools/parameters/dynamodb';constdynamoDBProvider=newDynamoDBProvider({tableName:'my-table',keyAttr:'key',sortAttr:'sort',valueAttr:'val',});exportconsthandler=async():Promise<void>=>{constvalue=awaitdynamoDBProvider.get('my-parameter');console.log(value);};

Create your own provider

You can create your own custom parameter store provider by extending the BaseProvider class, and implementing the get() and getMultiple() methods, as well as its respective _get() and _getMultiple() private methods to retrieve a single, or multiple parameters from your custom store.

All caching logic is handled by the BaseProvider, and provided that the return types of your store are compatible with the ones used in the BaseProvider, all transformations will also work as expected.

Here's an example of implementing a custom parameter store using an external service like HashiCorp Vault, a widely popular key-value secret storage.

Provider usageProvider implementationProvider types

import{Logger}from'@aws-lambda-powertools/logger';import{HashiCorpVaultProvider}from'./customProviderVault.js';constlogger=newLogger({serviceName:'serverless-airline'});constsecretsProvider=newHashiCorpVaultProvider({url:'https://vault.example.com:8200/v1',token:process.env.ROOT_TOKEN??'',rootPath:'kv',});// Retrieve a secret from HashiCorp Vaultconstsecret=awaitsecretsProvider.get<{foo:'string'}>('my-secret');constres=awaitfetch('https://example.com/api',{method:'POST',headers:{'Content-Type':'application/json',Authorization:`Bearer ${secret?.foo}`,},body:JSON.stringify({data:'example'}),});logger.debug('res status',{status:res.status});

import{BaseProvider}from'@aws-lambda-powertools/parameters/base';import{GetParameterError}from'@aws-lambda-powertools/parameters/errors';importtype{HashiCorpVaultGetOptions,HashiCorpVaultProviderOptions,}from'./customProviderVaultTypes.js';classHashiCorpVaultProviderextendsBaseProvider{readonly#baseUrl:string;readonly#token:string;readonly#rootPath?:string;readonly#timeout:number;readonly#abortController:AbortController;/** * It initializes the HashiCorpVaultProvider class. * * @param config - The configuration object. */publicconstructor(config:HashiCorpVaultProviderOptions){super({});const{url,token,rootPath,timeout}=config;this.#baseUrl=url;this.#rootPath=rootPath??'secret';this.#timeout=timeout??5000;this.#token=token;this.#abortController=newAbortController();}/** * Retrieve a secret from HashiCorp Vault. * * You can customize the retrieval of the secret by passing options to the function: * * `maxAge` - The maximum age of the value in cache before fetching a new one (in seconds) (default: 5) * * `forceFetch` - Whether to always fetch a new value from the store regardless if already available in cache * * `sdkOptions` - Extra options to pass to the HashiCorp Vault SDK, e.g. `mount` or `version` * * @param name - The name of the secret * @param options - Options to customize the retrieval of the secret */publicasyncget<TextendsRecord<string,unknown>>(name:string,options?:HashiCorpVaultGetOptions):Promise<T|undefined>{returnsuper.get(name,options)asPromise<Record<string,unknown>|undefined>asPromise<T|undefined>;}/** * Retrieving multiple parameter values is not supported with HashiCorp Vault. */publicasyncgetMultiple(path:string,_options?:unknown):Promise<void>{awaitsuper.getMultiple(path);}/** * Retrieve a secret from HashiCorp Vault. * * @param name - The name of the secret * @param options - Options to customize the retrieval of the secret */protectedasync_get(name:string,options?:HashiCorpVaultGetOptions):Promise<Record<string,unknown>>{const{sdkOptions}=options??{};constmount=sdkOptions?.mount??this.#rootPath;constversion=sdkOptions?.version?`?version=${sdkOptions?.version}`:'';setTimeout(()=>{this.#abortController.abort();},this.#timeout);constres=awaitfetch(`${this.#baseUrl}/${mount}/data/${name}${version}`,{headers:{'X-Vault-Token':this.#token},method:'GET',signal:this.#abortController.signal,});if(!res.ok){thrownewGetParameterError(`Failed to fetch secret ${res.statusText}`);}constresponse=awaitres.json();returnresponse.data.data;}/** * Retrieving multiple parameter values from HashiCorp Vault is not supported. * * @throws Not Implemented Error. */protectedasync_getMultiple(_path:string,_options?:unknown):Promise<Record<string,unknown>|undefined>{thrownewGetParameterError('Method not implemented.');}}export{HashiCorpVaultProvider};

importtype{GetOptionsInterface}from'@aws-lambda-powertools/parameters/base/types';/** * Options for the HashiCorpVaultProvider class constructor. * * @param {string} url - Indicate the server name/IP, port and API version for the Vault instance, all paths are relative to this one. * @param {string} token - The Vault token to use for authentication. * */interfaceHashiCorpVaultProviderOptions{/** * Indicate the server name/IP, port and API version for the Vault instance, all paths are relative to this one. * @example 'https://vault.example.com:8200/v1' */url:string;/** * The Vault token to use for authentication. */token:string;/** * The root path to use for the secret engine. Defaults to `secret`. */rootPath?:string;/** * The timeout in milliseconds for the HTTP requests. Defaults to `5000`. * @example 10000 * @default 5000 */timeout?:number;}typeHashiCorpVaultReadKVSecretOptions={/** * The mount point of the secret engine to use. Defaults to `secret`. * @example 'kv' */mount?:string;/** * The version of the secret to retrieve. Defaults to `undefined`. * @example 1 */version?:number;};interfaceHashiCorpVaultGetOptionsextendsGetOptionsInterface{/** * The Parameters utility does not support transforming `Record<string, unknown>` values as returned by the HashiCorp Vault SDK. */transform?:never;sdkOptions?:HashiCorpVaultReadKVSecretOptions;}exporttype{HashiCorpVaultProviderOptions,HashiCorpVaultGetOptions};

Deserializing values with transform parameter

For parameters stored in JSON or Base64 format, you can use the transform argument for deserialization.

Info

The transform argument is available across all providers, including the high level functions.

High level functionsProviders

import{getParameter}from'@aws-lambda-powertools/parameters/ssm';exportconsthandler=async():Promise<void>=>{constvalueFromJson=awaitgetParameter('/my/json/parameter',{transform:'json',});console.log(valueFromJson);};

import{SecretsProvider}from'@aws-lambda-powertools/parameters/secrets';constsecretsProvider=newSecretsProvider();exportconsthandler=async():Promise<void>=>{// Transform a JSON stringconstjson=awaitsecretsProvider.get('my-secret-json',{transform:'json',});console.log(json);// Transform a Base64 encoded string (e.g. binary)constbinary=awaitsecretsProvider.getMultiple('my-secret-binary',{transform:'binary',});console.log(binary);};

Partial transform failures with getMultiple()

If you use transform with getMultiple(), you can have a single malformed parameter value. To prevent failing the entire request, the method will return an undefined value for the parameters that failed to transform.

You can override this by setting the throwOnTransformError argument to true. If you do so, a single transform error will throw a TransformParameterError error.

For example, if you have three parameters, /param/a, /param/b and /param/c, but /param/c is malformed:

import{SSMProvider}from'@aws-lambda-powertools/parameters/ssm';constparametersProvider=newSSMProvider();exportconsthandler=async():Promise<void>=>{/** * This will display: * /param/a: [some value] * /param/b: [some value] * /param/c: undefined */constparameters=awaitparametersProvider.getMultiple('/param',{transform:'json',});for(const[key,value]ofObject.entries(parameters||{})){console.log(`${key}: ${value}`);}try{// This will throw a TransformParameterErrorconstparameters2=awaitparametersProvider.getMultiple('/param',{transform:'json',throwOnTransformError:true,});for(const[key,value]ofObject.entries(parameters2||{})){console.log(`${key}: ${value}`);}}catch(err){console.error(err);}};

Auto-transform values on suffix

If you use transform with getMultiple(), you might want to retrieve and transform parameters encoded in different formats.

You can do this with a single request by using transform: 'auto'. This will instruct any provider to infer its type based on the suffix and transform it accordingly.

Info

transform: 'auto' feature is available across all providers, including the high level functions.

import{SSMProvider}from'@aws-lambda-powertools/parameters/ssm';constparametersProvider=newSSMProvider();exportconsthandler=async():Promise<void>=>{constvalues=awaitparametersProvider.getMultiple('/param',{transform:'auto',});for(const[key,value]ofObject.entries(values||{})){console.log(`${key}: ${value}`);}};

For example, if you have three parameters: two with the following suffixes .json and .binary and one without any suffix:

Parameter name	Parameter value
/param/a	[some encoded value]
/param/a.json	[some encoded value]
/param/a.binary	[some encoded value]

The return of await parametersProvider.getMultiple('/param', transform: 'auto'); call will be an object like:

{"a":[someencodedvalue],"a.json":[somedecodedvalue],"b.binary":[somedecodedvalue]}

The two parameters with a suffix will be decoded, while the one without a suffix will be returned as is.

Passing additional SDK arguments

You can use a special sdkOptions object argument to pass any supported option directly to the underlying SDK method.

import{SecretsProvider}from'@aws-lambda-powertools/parameters/secrets';importtype{GetSecretValueCommandInput}from'@aws-sdk/client-secrets-manager';constsecretsProvider=newSecretsProvider();exportconsthandler=async():Promise<void>=>{constsdkOptions:Partial<GetSecretValueCommandInput>={VersionId:'e62ec170-6b01-48c7-94f3-d7497851a8d2',};/** * The 'VersionId' argument will be passed to the underlying * `GetSecretValueCommand` call. */constsecret=awaitsecretsProvider.get('my-secret',{sdkOptions});console.log(secret);};

Here is the mapping between this utility's functions and methods and the underlying SDK:

Provider	Function/Method	Client name	Function name
SSM Parameter Store	getParameter	@aws-sdk/client-ssm	GetParameterCommand
SSM Parameter Store	getParameters	@aws-sdk/client-ssm	GetParametersByPathCommand
SSM Parameter Store	SSMProvider.get	@aws-sdk/client-ssm	GetParameterCommand
SSM Parameter Store	SSMProvider.getMultiple	@aws-sdk/client-ssm	GetParametersByPathCommand
SSM Parameter Store	setParameter	@aws-sdk/client-ssm	PutParameterCommand
SSM Parameter Store	SSMProvider.set	@aws-sdk/client-ssm	PutParameterCommand
Secrets Manager	getSecret	@aws-sdk/client-secrets-manager	GetSecretValueCommand
Secrets Manager	SecretsProvider.get	@aws-sdk/client-secrets-manager	GetSecretValueCommand
AppConfig	AppConfigProvider.get	@aws-sdk/client-appconfigdata	StartConfigurationSessionCommand & GetLatestConfigurationCommand
AppConfig	getAppConfig	@aws-sdk/client-appconfigdata	StartConfigurationSessionCommand & GetLatestConfigurationCommand
DynamoDB	DynamoDBProvider.get	@aws-sdk/client-dynamodb	GetItemCommand
DynamoDB	DynamoDBProvider.getMultiple	@aws-sdk/client-dynamodb	QueryCommand

Bring your own AWS SDK v3 client

You can use the awsSdkV3Client parameter via any of the available Provider Classes.

Provider	Client
SSMProvider	new SSMClient();
SecretsProvider	new SecretsManagerClient();
AppConfigProvider	new AppConfigDataClient();
DynamoDBProvider	new DynamoDBClient();

When is this useful?

Injecting a custom AWS SDK v3 client allows you to apply tracing or make unit/snapshot testing easier, including SDK customizations.

SSMProviderSecretsProviderAppConfigProviderDynamoDBProvider

import{SSMProvider}from'@aws-lambda-powertools/parameters/ssm';import{SSMClient}from'@aws-sdk/client-ssm';// construct your clients with any custom configurationconstssmClient=newSSMClient({region:'us-east-1'});// pass the client to the providerconstparametersProvider=newSSMProvider({awsSdkV3Client:ssmClient});exportconsthandler=async():Promise<void>=>{// Retrieve a single parameterconstparameter=awaitparametersProvider.get('/my/parameter');console.log(parameter);};

import{SecretsProvider}from'@aws-lambda-powertools/parameters/secrets';import{SecretsManagerClient}from'@aws-sdk/client-secrets-manager';// construct your clients with any custom configurationconstsecretsManagerClient=newSecretsManagerClient({region:'us-east-1'});// pass the client to the providerconstsecretsProvider=newSecretsProvider({awsSdkV3Client:secretsManagerClient,});exportconsthandler=async():Promise<void>=>{// Retrieve a single secretconstsecret=awaitsecretsProvider.get('my-secret');console.log(secret);};

import{AppConfigProvider}from'@aws-lambda-powertools/parameters/appconfig';import{AppConfigDataClient}from'@aws-sdk/client-appconfigdata';// construct your clients with any custom configurationconstappConfigClient=newAppConfigDataClient({region:'us-east-1'});// pass the client to the providerconstconfigsProvider=newAppConfigProvider({application:'my-app',environment:'my-env',awsSdkV3Client:appConfigClient,});exportconsthandler=async():Promise<void>=>{constconfig=awaitconfigsProvider.get('my-config');console.log(config);};

import{DynamoDBProvider}from'@aws-lambda-powertools/parameters/dynamodb';import{DynamoDBClient}from'@aws-sdk/client-dynamodb';// construct your clients with any custom configurationconstdynamoDBClient=newDynamoDBClient({region:'us-east-1'});// pass the client to the providerconstvaluesProvider=newDynamoDBProvider({tableName:'my-table',awsSdkV3Client:dynamoDBClient,});exportconsthandler=async():Promise<void>=>{// Retrieve a single valueconstvalue=awaitvaluesProvider.get('my-value');console.log(value);};

Customizing AWS SDK v3 configuration

The clientConfig parameter enables you to pass in a custom config object when constructing any of the built-in provider classes.

Tip

You can use a custom session for retrieving parameters cross-account/region and for snapshot testing.

When using VPC private endpoints, you can pass a custom client altogether. It's also useful for testing when injecting fake instances.

import{SSMProvider}from'@aws-lambda-powertools/parameters/ssm';importtype{SSMClientConfig}from'@aws-sdk/client-ssm';constclientConfig:SSMClientConfig={region:'us-east-1'};constparametersProvider=newSSMProvider({clientConfig});exportconsthandler=async():Promise<void>=>{// Retrieve a single parameterconstvalue=awaitparametersProvider.get('/my/parameter');console.log(value);};

Testing your code

Mocking parameter values

For unit testing your applications, you can mock the calls to the parameters utility to avoid calling AWS APIs. This can be achieved in a number of ways - in this example, we mock the module import to patch the getParameters function.

handler.test.tshandler.ts

import{afterEach,describe,expect,it,vi}from'vitest';import{handler}from'./testingYourCodeFunctionsHandler.js';constmocks=vi.hoisted(()=>({getParameter:vi.fn(),}));vi.mock('@aws-lambda-powertools/parameters/ssm',async(importOriginal)=>({...(awaitimportOriginal<typeofimport('@aws-lambda-powertools/parameters/ssm')>()),getParameter:mocks.getParameter,}));describe('Function tests',()=>{afterEach(()=>{vi.clearAllMocks();});it('returns the correct response',async()=>{// Preparemocks.getParameter.mockResolvedValueOnce('my/param');// Actconstresult=awaithandler({},{});// Assessexpect(result).toEqual({value:'my/param',});});});

import{getParameter}from'@aws-lambda-powertools/parameters/ssm';exportconsthandler=async(_event:unknown,_context:unknown):Promise<Record<string,unknown>>=>{constparameter=awaitgetParameter('my/param');return{value:parameter,};};

With this pattern in place, you can customize the return values of the mocked function to test different scenarios without calling AWS APIs.

A similar pattern can be applied also to any of the built-in provider classes - in this other example, we use spies to patch the get function of the AppConfigProvider class. This is useful also when you want to test that the correct arguments are being passed to the Parameters utility.

handler.test.tshandler.ts

import{AppConfigProvider}from'@aws-lambda-powertools/parameters/appconfig';import{Uint8ArrayBlobAdapter}from'@smithy/util-stream';import{afterEach,describe,expect,it,vi}from'vitest';import{handler}from'./testingYourCodeFunctionsHandler.js';describe('Function tests',()=>{constproviderSpy=vi.spyOn(AppConfigProvider.prototype,'get');afterEach(()=>{vi.clearAllMocks();});it('retrieves the config once and uses the correct name',async()=>{// PrepareconstexpectedConfig={feature:{enabled:true,name:'paywall',},};providerSpy.mockResolvedValueOnce(Uint8ArrayBlobAdapter.fromString(JSON.stringify(expectedConfig)));// Actconstresult=awaithandler({},{});// Assessexpect(result).toStrictEqual({value:expectedConfig});expect(providerSpy).toHaveBeenCalledTimes(1);expect(providerSpy).toHaveBeenCalledWith('my-config');});});

import{AppConfigProvider}from'@aws-lambda-powertools/parameters/appconfig';constprovider=newAppConfigProvider({environment:'dev',application:'my-app',});exportconsthandler=async(_event:unknown,_context:unknown):Promise<Record<string,unknown>>=>{constconfig=awaitprovider.get('my-config');return{value:config,};};

For when you want to mock the AWS SDK v3 client directly, we recommend using the aws-sdk-client-mock and aws-sdk-client-mock-vitest libraries. This is useful when you want to test how your code behaves when the AWS SDK v3 client throws an error or a specific response.

handler.test.tshandler.ts

import{GetSecretValueCommand,ResourceNotFoundException,SecretsManagerClient,}from'@aws-sdk/client-secrets-manager';import{mockClient}from'aws-sdk-client-mock';import{afterEach,describe,expect,it,vi}from'vitest';import{handler}from'./testingYourCodeFunctionsHandler.js';import'aws-sdk-client-mock-vitest';describe('Function tests',()=>{constclient=mockClient(SecretsManagerClient);afterEach(()=>{vi.clearAllMocks();client.reset();});it('returns the correct error message',async()=>{// Prepareclient.on(GetSecretValueCommand).rejectsOnce(newResourceNotFoundException({$metadata:{httpStatusCode:404,},message:'Unable to retrieve secret',}));// Actconstresult=awaithandler({},{});// Assessexpect(result).toStrictEqual({message:'Unable to retrieve secret'});});});

import{getSecret}from'@aws-lambda-powertools/parameters/secrets';exportconsthandler=async(_event:unknown,_context:unknown):Promise<Record<string,unknown>>=>{try{constparameter=awaitgetSecret('my-secret');return{value:parameter,};}catch(error){return{message:'Unable to retrieve secret',};}};

Clearing cache

Parameters utility caches all parameter values for performance and cost reasons. However, this can have unintended interference in tests using the same parameter name.

Within your tests, you can use clearCache method available in every provider. When using multiple providers or higher level functions like getParameter, use the clearCaches standalone function to clear cache globally.

handler.test.ts

import{clearCaches}from'@aws-lambda-powertools/parameters';import{afterEach,describe}from'vitest';describe('Function tests',()=>{afterEach(()=>{clearCaches();});// ...});