In-Depth Guide to Amazon ECR: Learning Practical Container Registry Design Through Comparison with Artifact Registry and Azure Container Registry

Introduction

Amazon ECR (Amazon Elastic Container Registry) is a fully managed container image registry provided by AWS. It can store and manage not only Docker images, but also OCI images and OCI-compatible artifacts. It includes many features commonly needed in production operations, such as IAM-based access control, vulnerability scanning, lifecycle policies, replication, and pull through cache. AWS official documentation describes ECR as a secure, scalable, and reliable managed container image registry service that supports Docker images, OCI images, and OCI-compatible artifacts.

This topic is useful not only for infrastructure engineers working with ECS, EKS, Fargate, or Kubernetes platforms. For application development teams as well, a container registry is more than just a “warehouse for images.” Decisions such as which tags to retain, who can push images, where vulnerabilities are checked, how base image updates are tracked, and how images are distributed to other regions or accounts directly affect release speed and security. One of ECR’s strengths is that it naturally fits into AWS permission, audit, and network design.

Good comparison targets are Google Cloud’s Artifact Registry and Azure’s Azure Container Registry (ACR). Artifact Registry is a service that centrally stores artifacts as part of Google Cloud’s integrated experience. It is described as a “universal package manager” that handles not only containers, but also multiple types of packages. Google Cloud also recommends migrating from the older Container Registry to Artifact Registry, making Artifact Registry the current standard choice. Azure Container Registry is a private registry for all kinds of container deployments, providing image and related artifact storage and management, build automation in Azure, geo-replication, Private Link, and more.

To state the conclusion first, if you operate containers on AWS, Amazon ECR is a very natural and easy-to-use choice. On the other hand, if you want to centrally manage packages beyond containers, Artifact Registry is attractive, and if you want registry operations close to Microsoft / Azure infrastructure, ACR is easier to organize. In other words, the question is not which one is the best overall. You are less likely to fail if you choose based on which cloud delivery platform you align with, what you put in the registry, and how much you want to automate.

1. What Is Amazon ECR?

Amazon ECR is a service for securely storing and distributing container images and OCI artifacts, centered on a private registry provided for each AWS account. Official documentation explains that each AWS account is provided with a default private registry, allowing users to manage private image repositories on a highly available and scalable architecture. If public distribution is needed, Amazon ECR Public is also available as a separate service.

What matters here is not to think of ECR merely as an “internal version of Docker Hub.” In practice, a registry is the entry point of the software supply chain. It becomes the center for managing which image was built when, which tag maps to which commit, how vulnerabilities are evaluated, who can push to production repositories, and how images are replicated across regions or accounts. Because ECR provides IAM-based resource permissions, scanning, lifecycle policies, replication, and more, it is easier to build operations that go beyond simple storage.

ECR is also highly attractive because it sits very close to AWS container execution platforms. When combined with ECS, EKS, and Fargate, permissions, authentication, regional design, and auditing align naturally. You do not need to introduce a registry product with a completely different design philosophy. This ability to “fit naturally into the AWS flow” may seem subtle, but it is operationally very important.

2. Key ECR Features: These Four Matter in Practice

2-1. Lifecycle Policies

ECR lifecycle policies automatically organize old images and unnecessary tags. AWS official documentation explains that lifecycle policies allow you to define rules for cleaning up unused images and preview their impact. It also states that archive or expire actions based on policies are applied within up to 24 hours and are recorded in CloudTrail.

This is extremely important in practice. In container development, tagged images tend to increase with every CI run. If left unmanaged, it becomes unclear which images are active and which are unnecessary. As a result, not only registry storage capacity, but also rollback decisions and vulnerability response scope become difficult to understand. Therefore, when introducing ECR, the first thing to do is not necessarily push automation, but to clarify “how many generations to retain,” “how to handle latest,” and “whether production tags must never be deleted,” then convert that into lifecycle policies.

2-2. Vulnerability Scanning

ECR includes image scanning features. AWS official documentation explains that ECR provides software vulnerability scanning and supports both basic scanning and enhanced scanning. Basic scanning supports scanning on push and manual scans, and an image can be scanned once every 24 hours. Enhanced scanning is configured at the registry and region level.

The practical point here is that “having scanning” does not automatically mean “being secure.” Scan results only matter when they are incorporated into operations. For example, you need rules such as whether deployment stops when critical vulnerabilities are found, whether a grace period is allowed, and whether base image updates should be automatically encouraged. ECR provides the scanning function, but as an organization, the more important first step is deciding “from which severity level we stop releases.”

2-3. Replication

ECR private registries support cross-Region and cross-account replication. AWS official documentation explains that by configuring a permissions policy in the destination account, private repositories can be replicated from the source registry to another account or region.

This feature is useful for multi-account operations and disaster recovery. For example, it becomes easier to distribute images built in a development account to a production account, or to pre-replicate artifacts built in the Tokyo region to Osaka. Rather than “creating separate registries for each environment,” designing around “replication from a trusted source” is clearer from a supply chain management perspective.

2-4. Pull Through Cache

ECR can synchronize and cache content from upstream registries into a private registry using pull through cache rules. AWS official documentation explains that Amazon ECR Public, the Kubernetes container image registry, Quay, and others can be configured as upstream sources.

This is very useful when you want to reduce dependency on external registries. For example, if a production cluster pulls from external public registries every time, there are concerns around availability, speed, and auditing. By caching through ECR, you improve control and visibility over distribution routes and make it easier to incorporate security scanning and access control.

3. Comparison with GCP Artifact Registry

Artifact Registry is Google Cloud’s integrated artifact registry. Official documentation describes Artifact Registry as a “universal package manager” that centrally stores artifacts and build dependencies, handling not only container images but also non-container artifacts. Google Cloud also recommends Artifact Registry as the migration destination from Container Registry.

At this point, the difference from ECR becomes clear. ECR is very strong as a container registry, while Artifact Registry is better understood as a centralized management platform for multiple artifact types, including containers. If your organization strongly requires “managing not only containers, but also language packages and dependencies under the same policy,” Artifact Registry’s design philosophy is very attractive.

Artifact Registry includes remote repositories and virtual repositories. The official overview explains that remote repositories can cache upstream public sources and help with vulnerability scanning and dependency information management, while virtual repositories allow multiple repositories to be treated as a single endpoint. In addition, when the Container Scanning API is enabled, images pushed to Artifact Registry are automatically scanned. Release notes also state that since 2024, scanning can be enabled or disabled at the repository level.

In practical terms:

• ECR is natural when you want to organize an AWS container supply line cleanly
• Artifact Registry is attractive when you want centralized management of containers plus other packages

If you only look at container registries, ECR is very easy to understand. But when you broaden the view to an organization-wide artifact strategy, Artifact Registry has a wider scope.

4. Comparison with Azure Container Registry

Azure Container Registry (ACR) is Azure’s private container registry, used to build, store, and manage container images and related artifacts. Official documentation describes ACR as a private registry service that covers build, storage, and management. In addition, ACR Tasks enables on-demand builds on Azure, as well as automated builds triggered by source updates, base image updates, or timers.

A noticeable difference from ECR is the strength of built-in registry-side build functionality. ECR itself is not a build execution platform and is typically used together with external CI/CD or build pipelines. ACR, on the other hand, makes it easier to automate builds, rebuilds, and base image tracking near the registry through Tasks. In particular, the ability to automatically rebuild dependent application images when base images are updated is very compatible with security operations.

ACR’s Premium SKU also supports geo-replication, Private Link, and higher throughput and API concurrency. Azure’s SKU documentation clearly states that there are three tiers—Basic, Standard, and Premium—and that geo-replication and Private Link are supported in Premium. When geo-replication is enabled, pushed images are synchronized to each geo-replica.

For field use, the difference can be summarized as follows:

• ECR is a container registry that naturally fits AWS
• ACR makes it easier to complete registry operations, build automation, and geo-replication inside Azure

For organizations that want to stay within Microsoft / Azure infrastructure, the ACR experience is quite straightforward. Conversely, if you are thinking together with an AWS deployment platform, ECR is the more natural choice.

5. How to Think About Pricing

ECR pricing is relatively easy to understand, mainly based on stored data volume and data transfer. AWS pricing pages and FAQs explain that there are no upfront fees or commitments, and charges are based on the amount of data stored in private / public repositories and data transfer to the internet and other destinations. For example, cases are shown where data transfer out is not charged when ECS on EC2 or Fargate pulls images within the same region.

Artifact Registry pricing is described on the official pricing page as mainly based on storage, data transfer, and vulnerability scanning. In other words, it is similar to ECR, but scanning is more visibly represented in the pricing structure.

ACR is based on Basic / Standard / Premium SKUs, with differences in daily pricing, included storage, and features. Azure’s pricing page organizes included storage and supported features by Basic / Standard / Premium.

To translate this into very practical terms:

• ECR: Costs increase mainly with storage and transfer volume
• Artifact Registry: Consider storage, transfer, and scanning together
• ACR: First choose the SKU, then consider capacity and features

Examples of Patterns That Increase Costs

• Keeping tags from every CI run and allowing storage volume to grow
• Frequent pulls to other regions or over the internet
• Expanding scan targets too broadly, increasing both operational noise and cost
• Using an upper-tier ACR SKU even when Premium features are unnecessary

Therefore, in any cloud, deciding what to retain and for how many generations is the first step in cost optimization. A registry may look like a small component, but in organizations with active CI/CD, costs quietly grow if it is not organized.

6. Cases Where Amazon ECR Is Especially Suitable

Amazon ECR fits most naturally for teams that operate containers mainly on ECS / EKS / Fargate on AWS. Image storage, access control, deployment, auditing, and replication can all be aligned within the AWS context, avoiding the need to span an external registry or another cloud’s authentication system.

It is also suitable for teams that want to strengthen control over container distribution. By combining pull through cache, image scanning, lifecycle policies, and cross-account replication, teams can reduce dependency on public registries while improving visibility into their software supply line. This becomes increasingly valuable as internal security and audit requirements grow stronger.

ECR is also a good fit for organizations that want to properly organize containers first. Rather than expanding the scope broadly like Artifact Registry, if you want to focus first on managing Docker / OCI images and related artifacts and improving their quality, ECR is very easy to understand. It also pairs well with the approach of stabilizing the container platform first, then expanding to other package management later.

7. Common Mistakes and How to Avoid Them

7-1. Not Deciding a Tag Strategy

If you operate only with latest, mix commit SHAs and release tags, or treat production tags and CI tags the same way, rollback and vulnerability response become difficult later. After introducing ECR, first decide tag naming rules and retention policies, then convert them into lifecycle policies.

7-2. Only Looking at Scan Results Without Operationalizing Them

Even if vulnerability scanning is enabled, without response criteria you often end up in a state where “issues are found, but nobody stops anything.” Scanning becomes useful when severity thresholds, exception requests, and base image update policies are decided in advance.

7-3. Continuing Direct Dependency on Public Registries

This is convenient in early development, but if production clusters pull directly from external registries every time, availability, auditing, and speed remain concerns. Using pull through cache or mirroring to a private registry helps move the supply route closer to your own organization and stabilizes operations.

7-4. Underestimating Differences Between Clouds

ECR, Artifact Registry, and ACR are all “container registries,” but Artifact Registry focuses on artifacts more broadly, ACR includes Tasks and Premium features, and ECR is strong in its integration with AWS container operations. Do not assume they are the same just because the names are similar. Choose based on which one fits your supply line.

Conclusion

Amazon ECR is a fully managed container registry that naturally fits AWS container operations. With private registry, public registry, lifecycle policies, image scanning, cross-Region / cross-account replication, pull through cache, and more, it is attractive not as a mere storage location, but as the core of a container supply line.

Artifact Registry is an integrated artifact platform that makes it easier to manage packages beyond containers and is the current standard choice on Google Cloud. ACR’s strengths are its basic private registry functions plus ACR Tasks, geo-replication in Premium SKU, Private Link, and the ability to build a container supply line within Azure.

In very practical terms:

• Want stable container operations on AWS → Amazon ECR
• Want integrated artifact management including non-container packages → Artifact Registry
• Want to organize build automation and geo-replication on Azure → Azure Container Registry

As a first step, even when choosing ECR, it is better not to build every repository all at once. Instead, start by preparing tag strategy, lifecycle policy, and scan operations for one production service. That alone can transform the registry from “just a warehouse” into an “explainable supply line.”

Reference Information

• Amazon ECR overview, OCI support, IAM integration, private/public registry.
• ECR lifecycle policies, scanning, pull through cache, and replication.
• Artifact Registry overview, migration recommendation, remote/virtual repositories, vulnerability scanning.
• Azure Container Registry overview, SKU, geo-replication, and Tasks.