Available default environment variables in AWS Lambda. Just copy&paste into your Node or Java project.

lambda-constants.js

/**
 * Contains the path to your Lambda function code.
 */
const LAMBDA_TASK_ROOT = process.env.LAMBDA_TASK_ROOT;

/**
 * The environment variable is set to one of the following options, depending on the runtime of the Lambda function:
 * AWS_Lambda_nodejs, AWS_Lambda_nodejs4.3, AWS_Lambda_nodejs6.10
 */
const AWS_EXECUTION_ENV = process.env.AWS_EXECUTION_ENV;

/**
 * Restricted to Lambda runtime-related artifacts. For example the aws-sdk for Node.js and boto3 for Python can be found under this path.
 */
const LAMBDA_RUNTIME_DIR = process.env.LAMBDA_RUNTIME_DIR;

/**
 * The AWS region where the Lambda function is executed.
 */
const AWS_REGION = process.env.AWS_REGION;

/**
 * The AWS region where the Lambda function is executed.
 */
const AWS_DEFAULT_REGION = process.env.AWS_DEFAULT_REGION;

/**
 * 	The name of Amazon CloudWatch Logs group where log streams containing your Lambda function logs are created.
 */
const AWS_LAMBDA_LOG_GROUP_NAME = process.env.AWS_LAMBDA_LOG_GROUP_NAME;

/**
 * The Amazon CloudWatch Logs streams containing your Lambda function logs.
 */
const AWS_LAMBDA_LOG_STREAM_NAME = process.env.AWS_LAMBDA_LOG_STREAM_NAME;

/**
 * The name of the Lambda function.
 */
const AWS_LAMBDA_FUNCTION_NAME = process.env.AWS_LAMBDA_FUNCTION_NAME;

/**
 * The size of the Lambda function in MB.
 */
const AWS_LAMBDA_FUNCTION_MEMORY_SIZE = process.env.AWS_LAMBDA_FUNCTION_MEMORY_SIZE;

/**
 * The version of the Lambda function.
 */
const AWS_LAMBDA_FUNCTION_VERSION = process.env.AWS_LAMBDA_FUNCTION_VERSION;

/**
 * The security credentials required to execute the Lambda function, depending on which runtime is used.
 * Different runtimes use a subset of these keys. They are generated via an IAM execution role specified for the function.
 */
const AWS_ACCESS_KEY = process.env.AWS_ACCESS_KEY;

/**
 * The security credentials required to execute the Lambda function, depending on which runtime is used.
 * Different runtimes use a subset of these keys. They are generated via an IAM execution role specified for the function.
 */
const AWS_ACCESS_KEY_ID = process.env.AWS_ACCESS_KEY_ID;

/**
 * The security credentials required to execute the Lambda function, depending on which runtime is used.
 * Different runtimes use a subset of these keys. They are generated via an IAM execution role specified for the function.
 */
const AWS_SECRET_KEY = process.env.AWS_SECRET_KEY;

/**
 * The security credentials required to execute the Lambda function, depending on which runtime is used.
 * Different runtimes use a subset of these keys. They are generated via an IAM execution role specified for the function.
 */
const AWS_SECRET_ACCESS_KEY = process.env.AWS_SECRET_ACCESS_KEY;

/**
 * The security credentials required to execute the Lambda function, depending on which runtime is used.
 * Different runtimes use a subset of these keys. They are generated via an IAM execution role specified for the function.
 */
const AWS_SESSION_TOKEN = process.env.AWS_SESSION_TOKEN;

/**
 * The security credentials required to execute the Lambda function, depending on which runtime is used.
 * Different runtimes use a subset of these keys. They are generated via an IAM execution role specified for the function.
 */
const AWS_SECURITY_TOKEN = process.env.AWS_SECURITY_TOKEN;

/**
 * Contains /usr/local/bin, /usr/bin or /bin for running executables.
 */
const PATH = process.env.PATH;

/**
 * Set to en_US.UTF-8. This is the Locale of the runtime.
 */
const LANG = process.env.LANG;

/**
 * Contains /lib64, /usr/lib64, LAMBDA_TASK_ROOT, LAMBDA_TASK_ROOT/lib. Used to store helper libraries and function code.
 */
const LD_LIBRARY_PATH = process.env.LD_LIBRARY_PATH;

/**
 * Set for the Node.js runtime. It contains LAMBDA_RUNTIME_DIR, LAMBDA_RUNTIME_DIR/node_modules, LAMBDA_TASK_ROOT.
 */
const NODE_PATH = process.env.NODE_PATH;

/**
 * The current local time. Defaults to :UTC.
 */
const TZ = process.env.TZ;


module.exports = {
    LAMBDA_TASK_ROOT,
    AWS_EXECUTION_ENV,
    LAMBDA_RUNTIME_DIR,
    AWS_REGION,
    AWS_DEFAULT_REGION,
    AWS_LAMBDA_LOG_GROUP_NAME,
    AWS_LAMBDA_LOG_STREAM_NAME,
    AWS_LAMBDA_FUNCTION_NAME,
    AWS_LAMBDA_FUNCTION_MEMORY_SIZE,
    AWS_LAMBDA_FUNCTION_VERSION,
    AWS_ACCESS_KEY,
    AWS_ACCESS_KEY_ID,
    AWS_SECRET_KEY,
    AWS_SECRET_ACCESS_KEY,
    AWS_SESSION_TOKEN,
    AWS_SECURITY_TOKEN,
    PATH,
    LANG,
    LD_LIBRARY_PATH,
    NODE_PATH,
    TZ
};

LambdaConstants.java

public class Constants {

    /**
     * Contains the path to your Lambda function code.
     */
    public static final String LAMBDA_TASK_ROOT = System.getenv("LAMBDA_TASK_ROOT");

    /**
     * The environment variable is set to one of the following options, depending on the runtime of the Lambda function:
     * AWS_Lambda_nodejs, AWS_Lambda_nodejs4.3, AWS_Lambda_nodejs6.10
     */
    public static final String AWS_EXECUTION_ENV = System.getenv("AWS_EXECUTION_ENV");

    /**
     * Restricted to Lambda runtime-related artifacts. For example the aws-sdk for Node.js and boto3 for Python can be found under this 
     * path.
     */
    public static final String LAMBDA_RUNTIME_DIR = System.getenv("LAMBDA_RUNTIME_DIR");

    /**
     * The AWS region where the Lambda function is executed.
     */
    public static final String AWS_REGION = System.getenv("AWS_REGION");

    /**
     * The AWS region where the Lambda function is executed.
     */
    public static final String AWS_DEFAULT_REGION = System.getenv("AWS_DEFAULT_REGION");

    /**
     * The name of Amazon CloudWatch Logs group where log streams containing your Lambda function logs are created.
     */
    public static final String AWS_LAMBDA_LOG_GROUP_NAME = System.getenv("AWS_LAMBDA_LOG_GROUP_NAME");

    /**
     * The Amazon CloudWatch Logs streams containing your Lambda function logs.
     */
    public static final String AWS_LAMBDA_LOG_STREAM_NAME = System.getenv("AWS_LAMBDA_LOG_STREAM_NAME");

    /**
     * The name of the Lambda function.
     */
    public static final String AWS_LAMBDA_FUNCTION_NAME = System.getenv("AWS_LAMBDA_FUNCTION_NAME");

    /**
     * The size of the Lambda function in MB.
     */
    public static final String AWS_LAMBDA_FUNCTION_MEMORY_SIZE = System.getenv("AWS_LAMBDA_FUNCTION_MEMORY_SIZE");

    /**
     * The version of the Lambda function.
     */
    public static final String AWS_LAMBDA_FUNCTION_VERSION = System.getenv("AWS_LAMBDA_FUNCTION_VERSION");

    /**
     * The security credentials required to execute the Lambda function, depending on which runtime is used.
     * Different runtimes use a subset of these keys. They are generated via an IAM execution role specified for the function.
     */
    public static final String AWS_ACCESS_KEY = System.getenv("AWS_ACCESS_KEY");

    /**
     * The security credentials required to execute the Lambda function, depending on which runtime is used.
     * Different runtimes use a subset of these keys. They are generated via an IAM execution role specified for the function.
     */
    public static final String AWS_ACCESS_KEY_ID = System.getenv("AWS_ACCESS_KEY_ID");

    /**
     * The security credentials required to execute the Lambda function, depending on which runtime is used.
     * Different runtimes use a subset of these keys. They are generated via an IAM execution role specified for the function.
     */
    public static final String AWS_SECRET_KEY = System.getenv("AWS_SECRET_KEY");

    /**
     * The security credentials required to execute the Lambda function, depending on which runtime is used.
     * Different runtimes use a subset of these keys. They are generated via an IAM execution role specified for the function.
     */
    public static final String AWS_SECRET_ACCESS_KEY = System.getenv("AWS_SECRET_ACCESS_KEY");

    /**
     * The security credentials required to execute the Lambda function, depending on which runtime is used.
     * Different runtimes use a subset of these keys. They are generated via an IAM execution role specified for the function.
     */
    public static final String AWS_SESSION_TOKEN = System.getenv("AWS_SESSION_TOKEN");

    /**
     * The security credentials required to execute the Lambda function, depending on which runtime is used.
     * Different runtimes use a subset of these keys. They are generated via an IAM execution role specified for the function.
     */
    public static final String AWS_SECURITY_TOKEN = System.getenv("AWS_SECURITY_TOKEN");

    /**
     * Contains /usr/local/bin, /usr/bin or /bin for running executables.
     */
    public static final String PATH = System.getenv("PATH");

    /**
     * Set to en_US.UTF-8. This is the Locale of the runtime.
     */
    public static final String LANG = System.getenv("LANG");

    /**
     * Contains /lib64, /usr/lib64, LAMBDA_TASK_ROOT, LAMBDA_TASK_ROOT/lib. Used to store helper libraries and function code.
     */
    public static final String LD_LIBRARY_PATH = System.getenv("LD_LIBRARY_PATH");

    /**
     * The current local time. Defaults to :UTC.
     */
    public static final String TZ = System.getenv("TZ");
}