Simple Terraform example with one DynamoDB table and one Lambda function

serverless.tf

provider "aws" { }

resource "aws_iam_role" "iam_for_lambda" {
  name = "iam_for_lambda"

  assume_role_policy = <<EOF
{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Action": "sts:AssumeRole",
      "Principal": {
        "Service": "lambda.amazonaws.com"
      },
      "Effect": "Allow",
      "Sid": ""
    }
  ]
}
EOF
}

resource "aws_lambda_function" "someFunction" {
  filename          = "lambda_function_someFunction.zip"
  function_name     = "lambda_function_name"
  role              = "${aws_iam_role.iam_for_lambda.arn}"
  handler           = "exports.handler"
  source_code_hash  = "${base64sha256(file("lambda_function_someFunction.zip"))}"
  runtime           = "nodejs6.10"
}

resource "aws_dynamodb_table" "someTable" {
  name              = "someTable"
  read_capacity     = 5
  write_capacity    = 5
  hash_key          = "id"
  range_key         = "version"
  stream_enabled    = true
  stream_view_type  = "NEW_AND_OLD_IMAGES"

  attribute {
    name = "id"
    type = "S"
  }

  attribute {
    name = "version"
    type = "N"
  }
}

resource "aws_lambda_event_source_mapping" "event_source_mapping" {
  batch_size        = 100
  event_source_arn  = "${aws_dynamodb_table.someTable.arn}"
  enabled           = true
  function_name     = "${aws_lambda_function.someFunction.function_name}"
  starting_position = "TRIM_HORIZON"
}