API网关和ALB都是AWS提供的托管服务，用于将请求路由到后端服务。但两者之间也存在一些区别和适用场景。

首先，API网关通常用于构建RESTful API，可以进行更高级的请求转换和路由，而ALB是一个传统的负载均衡器，也可以用于HTTP路由和负载均衡，但是功能比API网关要简单。

如果您需要构建复杂的API并需要完整的API管理工具，那么API网关是更好的选择。但如果您只需要进行HTTP负载均衡和路由，则ALB是更合适的选项。

以下是一些示例代码，演示了如何使用API网关和ALB：

API网关示例代码：

resource "aws_api_gateway_rest_api" "example" {
  name        = "example-api"
  description = "Example API"

  endpoint_configuration {
    types = ["REGIONAL"]
  }
}

resource "aws_api_gateway_resource" "example" {
  rest_api_id = aws_api_gateway_rest_api.example.id
  parent_id   = aws_api_gateway_rest_api.example.root_resource_id
  path_part   = "example"
}

resource "aws_api_gateway_method" "example" {
  rest_api_id   = aws_api_gateway_rest_api.example.id
  resource_id   = aws_api_gateway_resource.example.id
  http_method   = "GET"
  authorization = "NONE"

  request_parameters = {
    "method.request.querystring.foo" = true
  }

  request_models = {
    "application/json" = "{
      \"title\": \"Example\",
      \"type\": \"object\",
      \"properties\": {
        \"foo\": { \"type\": \"string\" }
      }
    }"
  }

  integration {
    type        = "HTTP_PROXY"
    uri         = "http://example.com/api"
    http_method = "GET"

    request_parameters = {
      "integration.request.querystring.foo" = "method.request.querystring.foo"
    }

    request_templates = {
      "application/json" = "{\n  \"foo\": \"$input.params('foo')\"\n}"
    }

    passthrough_behavior = "WHEN_NO_MATCH"
  }
}

resource "aws_api_gateway_stage" "example" {
  rest_api_id = aws_api_gateway_rest_api.example.id
  deployment_id = aws_api_gateway_deployment.example.id
  stage_name = "prod"

  # Enable X-Ray tracing for this stage
  xray_tracing_enabled = true
}
``