Migrate to Google Cloud: Assess and discover your workloads

Last reviewed 2023-06-07 UTC

This document can help you plan, design, and implement the assessment phase of your migration to Google Cloud. Discovering your apps and services inventory, and mapping their dependencies, can help you identify what you need to migrate and in what order. When planning and designing a migration to Google Cloud, you first need a deep knowledge of your current environment and of the apps and workloads to migrate.

This document is part of the following multi-part series about migrating to Google Cloud:

The following diagram illustrates the path of your migration journey.

Migration path with four phases.

The assess phase is the first phase in your migration to Google Cloud where you determine the requirements and dependencies to migrate your apps to Google Cloud.

This document is useful if you're planning a migration from an on-premises environment, a private hosting environment, another cloud provider, or if you're evaluating the opportunity to migrate and exploring what the assessment phase might look like.

The assessment phase is crucial for the success of your migration. You need to gain deep knowledge about the apps you want to migrate, their requirements, their dependencies, and about your current environment. You need to understand your starting point to successfully plan and execute a Google Cloud migration.

In this phase, you perform the following steps:

  1. Build a comprehensive inventory of your apps.
  2. Catalog your apps according to their properties and dependencies.
  3. Train and educate your teams on Google Cloud.
  4. Build an experiment and proof of concept on Google Cloud.
  5. Calculate the total cost of ownership (TCO) of the target environment.
  6. Choose the workloads that you want to migrate first.

Building an inventory of your apps

To scope your migration, you must first understand how many items, such as apps and hardware appliances, exist in your current environment, along with their dependencies. Building the inventory is a non-trivial task that requires a significant effort, especially when you don't have any automatic cataloging system in place. To have a comprehensive inventory, you need to use the expertise of the teams that are responsible for the design, deployment, and operation of each workload in your current environment, as well as the environment itself.

The inventory shouldn't be limited to apps only, but should at least contain the following:

  • Dependencies of each app, such as databases, message brokers, configuration storage systems, and other components.
  • Services supporting your app infrastructure, such as source repositories, continuous integration (CI) tools, and artifact repositories.
  • Servers, either virtual or physical, and runtime environments.
  • Physical appliances, such as network devices, firewalls, and other dedicated hardware.

When compiling this list, you should also gather information about each item, including:

  • Source code location and if you're able to modify this source code.
  • Deployment method for the workload in a runtime environment, for example, if you use an automated deployment pipeline or a manual one.
  • Network restrictions or security requirements.
  • IP address requirements.
  • How you're exposing the workload to clients.
  • Licensing requirements for any software or hardware.
  • How the workload authenticates against your identity and access management system.

For example, for each hardware appliance, you should know its detailed specifications, such as its name, vendor, technologies, and dependencies on other items in your inventory. For example:

  • Name: NAS Appliance
  • Vendor and model: Vendor Y, Model Z
  • Technologies: NFS, iSCSI
  • Dependencies: Network connectivity with Jumbo frames to VM compute hardware.

This list should also include non-technical information, for example, under which licensing terms you're allowed to use each item and any other compliance requirements. While some licenses let you deploy an app in a cloud environment, others explicitly forbid cloud deployment. Some licenses are assigned based on the number of CPUs or sockets in use, and these concepts might not be applicable when running on cloud technology. Some of your data might have restrictions regarding the geographical region where it's stored. Finally, some sensitive workloads can require sole tenancy.

Along with the inventory, it's useful to provide aids for a visual interpretation of the data you gathered. For example, you can provide a dependency graph and charts to highlight aspects of interest, such as how your apps are distributed in an automated or manual deployment process.

How to build your inventory

There are different ways to build an app inventory. While the quickest way to get started is to proceed manually, this approach can be difficult for a large production environment. Information in manually built inventories can quickly become outdated, and the resulting migration might fail because it was based on wrong assumptions.

Building the inventory is not a one-time exercise. If your current environment is highly dynamic, you should also spend effort in automating the inventory creation and maintenance, so you eventually have a consistent view of all the items in your environment at any given time. For information about how to build an inventory of your apps, see Migration Center: Start an asset discovery.

Google also partners with multiple companies to assist you in your migration journey. For more information, see Finding help.

Example of an app inventory

This example is an inventory of an environment supporting an ecommerce app. The inventory includes apps, dependencies, services supporting multiple apps, and hardware appliances.


For each app in the environment, the following table highlights the most important technologies, its deployment procedure, and other requirements.

Name Source code location Technologies Deployment procedure Other requirements Dependencies System resources requirements
Marketing website Corporate repository Angular frontend Automated Legal department must validate content Caching service 5 CPU cores
8 GB of RAM
Back office Corporate repository Java backend, Angular frontend Automated N/A SQL database 4 CPU cores
4 GB of RAM
Ecommerce app Proprietary app Vendor X
Model Y
Version 1.2.0
Manual Customer data must reside inside the European Union SQL database 10 CPU cores
32 GB of RAM
Enterprise resource planning (ERP) Proprietary app Vendor Z, Model C, Version 7.0 Manual N/A SQL database 10 CPU cores
32 GB of RAM
Stateless microservices Corporate repository Java Automated N/A Caching service 4 CPU cores
8 GB of RAM


The following table is an example of the dependencies of the apps listed in the inventory. These dependencies are necessary for the apps to correctly function.

Name Technologies Other requirements Dependencies System resources requirements
SQL database PostgreSQL Customer data must reside inside the European Union Backup and archive system 30 CPU cores
512 GB of RAM

Supporting services

In your environment, you might have services that support multiple apps. In this ecommerce example, there are the following services:

Name Technologies Other requirements Dependencies System resources requirements
Source code repositories Git N/A Backup and archive system 2 CPU cores
4 GB of RAM
Backup and archive system Vendor G, Model H, version 2.3.0 By law, long-term storage is required for some items N/A 10 CPU cores
8 GB of RAM
CI tool Jenkins N/A Source code repositories
artifact repository
backup and archive system
32 CPU cores
128 GB of RAM
Artifact repository Vendor A
Model N
Version 5.0.0
N/A Backup and archive system 4 CPU cores
8 GB of RAM
Batch processing service Cron jobs running inside the CI tool N/A CI tool 4 CPU cores
8 GB of RAM
Caching service Memcached
N/A N/A 12 CPU cores
50 GB of RAM


The example environment has the following hardware appliances:

Name Technologies Other requirements Dependencies System resources requirements
Firewall Vendor H
Model V
Instances of Server j Vendor K
Model B
Must be decommissioned because no longer supported N/A N/A
NAS Appliance Vendor Y
Model Z

Assess your deployment and operational processes

After you build the inventories of your workloads, we recommend that you assess your deployment and operational processes. Your deployment and operational processes are a fundamental part of the practices that prepare and maintain your production environment and the workloads that run there.

These processes may provision the necessary infrastructure, and build the artifacts that your workloads need, such as operating system packages, workload deployment packages, operating system images, and container images. For each workload, gather information about: how many artifacts it needs, the type of each artifact, how you're building these artifacts, how and where you're storing them, and how you're injecting runtime configuration so that these artifacts are reusable across environments.

After you assess your deployment and operational processes, we also recommend that you assess how these processes can facilitate your migration to Google Cloud, and how they help you reduce the scope and the risk of your migration. For example, you might refactor your artifact-build processes to store artifacts in both your source environment and in Google Cloud while the migration is underway. Having artifacts in both environments lets you focus on migrating your workloads and data from the source environment to Google Cloud without having to implement artifact-build processes in the target Google Cloud environment right from the start of the migration process.

Assess your infrastructure

After you assess your deployment and operational processes, we recommend that you assess the infrastructure that is currently supporting your workloads in the source environment.

To assess that infrastructure, consider the following:

  • The processes you adopted to provision the resources that the workload needs, such as infrastructure as code.
  • How you organized resources in your source environment. For example, some environments support a logical separation between resources using constructs that isolate groups of resources from each others, such as organizations and projects.
  • How you connected your environment to other environments, such as on-premises environments, and other cloud providers.

Categorizing your apps

After you complete the inventory, you need to organize your apps into different categories. This categorization can help you prioritize the apps to migrate according to their complexity and risk in moving to the cloud.

A catalog matrix should have one dimension for each assessment criterion you're considering in your environment. Choose a set of criteria that covers all the requirements of your environment, including the system resources each app needs. For example, you might be interested to know if an app has any dependencies, or if it's stateless or stateful. When you design the catalog matrix, consider that for each criteria you add, you are adding another dimension to represent. The resulting matrix might be difficult to visualize. A possible solution to this problem could be to use multiple smaller matrices, instead of a single, complex one.

Also, next to each app you should add a migration complexity indicator. This indicator estimates the difficulty rating to migrate each app. The granularity of this indicator depends on your environment. For a basic example, you might have three categories: easy to migrate, hard to migrate or cannot be migrated. To complete this activity, you need experts for each item in the inventory to estimate its migration complexity. Drivers of this migration complexity are unique to each business.

When the catalog is complete, you can also build visuals and graphs to help you and your team to quickly evaluate metrics of interest. For example, draw a graph that highlights how many components have dependencies or highlight the migration difficulty of each component.

For information about how to build an inventory of your apps, see Migration Center: Start an asset discovery.

Example of an app catalog

The following assessment criteria is used in this example, one for each matrix axis:

  1. How critical an app is to the business.
  2. Whether an app has dependencies, or is a dependency for other apps.
  3. Maximum allowable downtime for the app.
  4. How difficult an app is to be migrated.
Importance to the business Doesn't have dependencies or dependents Has dependencies or dependents Maximum allowable downtime Difficulty
Mission critical Stateless microservices 2 minutes Easy
ERP 24 hours Hard
Ecommerce app No downtime Hard
Hardware firewall No downtime Can't move
SQL database 10 minutes Easy
Source code repositories 12 hours Easy
Non-mission critical Marketing website 2 hours Easy
Backup and archive 24 hours Easy
Batch processing service 48 hours Easy
Caching service 30 minutes Easy
Back office 48 hours Hard
CI tool 24 hours Easy
Artifact repository 30 minutes Easy

To help you visualize the results in the catalog, you can build visuals and charts. The following chart highlights the migration difficulty:

Chart that visualizes the difficulty associated with moving apps to Google Cloud.

In the preceding chart, most of the apps are easy to move, while only three of them are hard to move, and one of them you can't move.

Educating your organization about Google Cloud

To take full advantage of Google Cloud, your organization needs to start learning about the services, products, and technologies that your business can use on Google Cloud. Your staff can begin with Google Cloud free trial accounts that contain credits to help them experiment and learn hands-on. Creating a free environment for testing and learning is critical to the learning experience of your staff.

You have several training options:

  1. Public and open resources: You can get started learning Google Cloud with free hands-on labs, video series, Cloud OnAir webinars, and Cloud OnBoard training events.
  2. In-depth courses: If you want a deeper understanding of how Google Cloud works, you can attend on-demand courses from Google Cloud Skills Boost or Google Cloud Training Specializations from Coursera that you can attend online at your own pace or classroom training by our world-wide authorized training partners. These courses typically span from one to several days.
  3. Role-based learning paths: You can train your engineers according to their role in your organization. For example, you can train your app developers or infrastructure operators how to best use Google Cloud services.

You can also certify your engineers' knowledge of Google Cloud with various certifications, at different levels:

  1. Associate certifications: A starting point for those new to Google Cloud that can open the door to professional certifications, such as the associate cloud engineer certification.
  2. Professional certifications: If you want to assess advanced design and implementation skills for Google Cloud from years of experience, you can get certifications, such as the professional cloud architect or the professional data engineer.
  3. Google Workspace certifications: You can demonstrate collaboration skills using Google Workspace tools with a Google Workspace certification.
  4. Apigee certifications: With the Apigee certified API engineer certification, you can demonstrate the ability to design and develop robust, secure, and scalable APIs.
  5. Google developers certifications: You can demonstrate development skills with the Associate Android developer (This certification is being updated) and mobile web specialist certifications.

In addition to training and certification, one of the best ways to get experience with Google Cloud is to begin using the product to build business proofs-of-concept.

Experimenting and designing proofs of concept

To show the value and efficacy of Google Cloud, consider designing and developing one or more proofs of concept (PoCs) for each category of app in your app catalog. Experimentation and testing let you validate assumptions and demonstrate the value of cloud to business leaders.

At a minimum, your PoC should include the following:

  • A comprehensive list of the use cases that your apps support, including uncommon ones and corner cases.
  • All the requirements for each use case, such as performance and scalability requirements, expected consistency guarantees, failover mechanisms, and network requirements.
  • A potential list of technologies and products that you want to investigate and test.

You should design PoCs and experiments to validate all the use cases on the list. Each experiment should have a precise validity context, scope, expected outputs, and measurable business impact.

For example, if one of your CPU-bound apps needs to quickly scale to satisfy peaks in demand, you can run an experiment to verify that a zone can create many virtual CPU cores, and how much time it takes to do so. If you experience a significant value-add, such as reducing new app scale-up time by 95% compared to your current environment, this can demonstrate instant business value.

If you're interested in evaluating how the performance of your on-premises databases compares to Cloud SQL, Spanner, Firestore, or Bigtable, you could implement a PoC where the same business logic uses different databases. This PoC gives you a low-risk opportunity to identify the right managed database solution for your workload across multiple benchmarks and operating costs.

If you want to evaluate the performance of the VM provisioning process in Google Cloud, you can use a third-party tool, such as PerfKit Benchmarker, and compare Google Cloud with other cloud providers. You can measure the end-to-end time to provision resources in the cloud, in addition to reporting on standard metrics of peak performance, including latency, throughput, and time-to-complete. For example, you might be interested in how much time and effort it takes to provision many Kubernetes clusters. PerfKit Benchmarker is an open source community effort involving over 500 participants, such as researchers, academic institutions, and companies, including Google.

Calculating total cost of ownership

When you have a clear view of the resources you need in the new environment, you can build a total cost of ownership model that lets you compare your costs on Google Cloud with the costs of your current environment.

When building this cost model, you should consider not only the costs for hardware and software, but also all the operational costs of running your own data center, such as power, cooling, maintenance, and other support services. Consider that it's also typically easier to reduce costs, thanks to the elastic scalability of Google Cloud resources, compared to a more rigid on-premises data center.

A commonly overlooked cost when considering cloud migrations is the use of a cloud network. In a data center, purchasing network infrastructure, such as routers and switches, and then running appropriate network cabling are one-time costs that let you use the entire capacity of the network. In a cloud environment, there are many ways that you might be billed for network utilization. For data intensive apps, or those that generate a large amount of network traffic, you might need to consider new architectures and network flows to lower networking costs in the cloud.

Google Cloud also provides a wide range of options for intelligent scaling of resources and costs. For example, in Compute Engine you can rightsize during your migration with Migrate for Compute Engine, or after VMs are already running, or building autoscaling groups of instances. These options can have a large impact on the costs of running services and should be explored to calculate the total cost of ownership (TCO).

To calculate the total cost of Google Cloud resources, you can use the price calculator.

Choosing the apps to migrate first

Now that you have an exhaustive view of your current environment, you need to complete your migration plan by choosing the initial order in which you want to migrate your apps. You can refine this order during the migration when you gain experience with Google Cloud and understand your environment and apps.

The apps you migrate first are the ones that let your teams build their knowledge and experience on Google Cloud. Greater cloud exposure and experience from your team can lower the risk of complications during the migration phase of your migration, and make subsequent migrations easier and quicker. For this reason, choosing the right first-movers is crucial for a successful migration. You can pick one app, or put many apps from across your apps matrix in your first-mover list.

The task of identifying the first-movers is complex, but here are some criteria to guide you:

  • Business value of the app.
  • If the app is deployed or run in a unique way compared to the rest of your infrastructure.
  • Teams responsible for development, deployment, and operations of the app.
  • Number, type, and scope of dependencies of the app.
  • Refactoring effort to make the app work in the new environment.
  • Compliance and licensing requirements of the app.
  • Availability and reliability requirements of the app.

Business value

Choosing an app that isn't business critical protects your main line of business, and decreases the impact on business from undiscovered risks and mistakes while your team is learning cloud technologies. For example, if you choose the component where the main financial transactions logic of your ecommerce app is implemented as a first-mover, any mistake during the migration might cause an impact on your main line of business. A better choice is the SQL database supporting your apps, or better yet, the staging database.

You should avoid rarely used apps. For example, if you choose an app that's used only a few times per year by a low number of users, while it's a low risk migration, it doesn't increase the momentum of your migration, and it can be hard to detect and respond to problems.

Edge cases

You should also avoid edge cases, so you can discover patterns that you can apply to other apps to migrate. A primary goal when selecting a first mover is to gain experience with common patterns in your organization so you can build a knowledge base. You can reapply what you learned with these first movers when migrating future apps later.

For example, if most of your apps are designed following a test-driven development methodology and are developed using the Python programming language, choosing an app with little test coverage and developed using the Java programming language, doesn't let you discover any pattern that you can apply when migrating the Python apps.


When choosing your first-movers, pay attention to the teams responsible for each app. The team responsible for a first-mover should be highly motivated, and eager to try Google Cloud and its services. Moreover, business leadership should have clear goals for the first-mover teams and actively work to sponsor and support them through the process.

For example, a high performing team that sits in the main office with a proven history of implementing modern development practices such as DevOps and disciplines such as site reliability engineering can be a good candidate. If they also have top-down leadership sponsors and clear goals around each apps migration, they can be a superb candidate.


Also, you should focus on apps that have the fewest number of dependencies, either from other apps or services. The migration of an app with no dependencies is easier when you have limited experience with Google Cloud.

If you have to choose apps that have dependencies on other components, pick the ones that are loosely coupled to their dependencies. If an app is already designed for the eventual unavailability of its dependencies, it can reduce the friction when migrating the app to the target environment. For example, loosely coupled candidates are apps that communicate by using a message broker, or that work offline, or are designed to tolerate the unavailability of the rest of the infrastructure.

Although there are strategies to migrate data of stateful apps, a stateless app rarely requires any data migration. Migrating a stateless app can be easier because you don't need to worry about a transitory phase where data is partially in your current environment and partially in your target environment. For example, stateless microservices are good first-mover candidates, because they don't rely on any local stateful data.

Refactoring effort

A first-mover should require a minimal amount of refactoring, so you can focus on the migration itself and on Google Cloud, instead of spending a large effort on changes to the code and configuration of your apps. The refactoring should focus on the necessary changes that allow your apps to run in the target environment instead of focusing on modernizing and optimizing your apps, which is tackled in later migration phases.

For example, an app that requires only configuration changes is a good first-mover, because you don't have to implement any change to codebase, and you can use the existing artifacts.

Licensing and compliance

Licenses also play a role in choosing the first-movers, because some of your apps might be licensed under terms that affect your migration. For example, some licenses explicitly forbid running apps in a cloud environment.

When examining the licensing terms, don't forget the compliance requirements because you might have sole tenancy requirements for some of your apps. For these reasons, you should choose apps that have the least amount of licensing and compliance restrictions as first-movers.

For example, your customers might have the legal right to choose in which region you store their data, or your customers' data might be restricted to a particular region.

Availability and reliability

Good first-movers are the ones that can afford a downtime caused by a cutover window. If you choose an app that has strict availability requirements, you have to implement a zero-downtime data migration strategy such as Y (writing and reading) or by developing a data-access microservice. While this approach is possible, it distracts your teams from gaining the necessary experience with Google Cloud, because they have to spend time to implement such strategies.

For example, the availability requirements of a batch processing engine can tolerate a longer downtime than the customer-facing app of your ecommerce site where your users finalize their transactions.

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