AWS Secrets Manager vs SSM Parameter Store for Storing Secrets

AWS Secrets Manager vs SSM Parameter Store for Storing Secrets#

If you’ve spent any time managing credentials and sensitive configuration in AWS, you’ve probably encountered an uncomfortable question: which service should I actually use? Both AWS Secrets Manager and AWS Systems Manager Parameter Store can encrypt and store secrets using KMS, and that similarity often leads developers to treat them interchangeably. In reality, they’re designed for different problems, and choosing the wrong tool can leave you with unnecessary operational overhead or missing critical functionality.

This article walks through the practical differences between these services, explores when to reach for each one, and helps you make an informed decision for your specific use case.

Understanding the Core Services#

Before diving into comparisons, let’s establish what we’re actually talking about. Secrets Manager and Parameter Store are both AWS systems management services, but they approach the problem of secure storage from different angles.

AWS Systems Manager Parameter Store is a general-purpose configuration management service that stores data in a hierarchical namespace. You can store plain text values, encrypted values (using KMS), and even retrieve parameters through a standardized API. Parameter Store integrates tightly with EC2, Lambda, and CloudFormation. It’s designed to be lightweight and cost-effective for managing configuration at scale.

AWS Secrets Manager is a purpose-built secrets management service that specializes in the lifecycle of sensitive credentials like database passwords, API keys, and OAuth tokens. While Parameter Store asks “how do I store this value safely?”, Secrets Manager asks “how do I manage the entire lifecycle of this credential, including rotation?”

The distinction matters more than the surface-level similarities suggest.

Encryption: A Shared Foundation#

Both services use AWS Key Management Service (KMS) to encrypt data at rest, so let’s address that similarity first. When you store a secret in Parameter Store using the SecureString type, you specify a KMS key (or use the default AWS-managed key), and the value is encrypted before storage. The same is true for Secrets Manager—your secret is encrypted using a KMS key you control or the AWS-managed default.

From an encryption perspective, both offer equivalent security. The difference is in what happens around that encryption: how credentials are rotated, how they’re audited, how they’re shared across accounts, and how they integrate with AWS services.

Automatic Rotation and Credential Lifecycle#

This is where Secrets Manager truly shines. Secrets Manager includes built-in support for automatic rotation of credentials. You can configure a Lambda function to rotate your secret on a schedule—for example, automatically changing an RDS database password every 30 days. Secrets Manager handles version management during rotation, ensuring your application can seamlessly transition from the old credential to the new one.

Here’s a conceptual flow: Secrets Manager calls your rotation Lambda, which connects to RDS and changes the password, updates the secret in Secrets Manager with the new password, and marks the rotation as complete. Your application reads the secret from Secrets Manager, and the service automatically provides the current version.

Parameter Store doesn’t include built-in rotation logic. If you need to rotate a parameter stored in Parameter Store, you have to orchestrate that rotation yourself—write the Lambda function, set up the EventBridge rule, manage versioning, and coordinate with your applications. It’s entirely possible, but it’s your responsibility to build and maintain that automation.

If your use case involves rotating credentials—especially database passwords or API keys—Secrets Manager is the natural choice. If you’re storing static configuration that doesn’t need rotation, Parameter Store is simpler and more cost-effective.

Integration with AWS Databases#

Secrets Manager has purpose-built integrations with RDS, Aurora, Redshift, and DocumentDB. When you create a secret for an RDS password, Secrets Manager can automatically rotate that secret by connecting to the database and changing the password. This is particularly valuable in compliance-heavy environments where regular credential rotation is mandatory.

Parameter Store, by contrast, has no special integration with databases. You can store a database password in Parameter Store, but you’re responsible for rotating it. This doesn’t make Parameter Store unsuitable for database passwords—many applications do exactly this—but it means you’re not getting AWS-managed rotation assistance.

If you’re managing RDS database credentials in AWS and need automatic rotation, Secrets Manager is the obvious fit. If you’re storing application configuration alongside that credential and want everything in one place, you’ll need to think about splitting them across services or accepting Parameter Store’s lack of automatic rotation.

Secrets Manager provides native support for cross-account secret sharing via resource-based policies. You can grant another AWS account permission to read a specific secret in your Secrets Manager vault, enabling secure credential sharing between accounts without copying secrets around or managing separate instances.

Parameter Store can be shared across accounts using IAM policies, but it’s less elegant. You need to ensure both accounts can access the same KMS key (the encryption key must have a policy allowing cross-account access), and you’re managing access control at the parameter level rather than through a dedicated resource policy.

For organizations with multiple AWS accounts that need to share secrets—a common pattern in larger enterprises—Secrets Manager’s cross-account resource policies are more straightforward and auditable.

Cost Considerations#

Parameter Store is significantly cheaper. You pay per API call and per parameter stored (with a generous free tier). If you’re storing dozens of parameters and reading them infrequently, the cost is negligible.

Secrets Manager charges per secret per month and per API call. A secret might cost $0.40 per month (though AWS occasionally runs promotions), plus API costs. If you’re rotating that secret monthly with Secrets Manager, you’re also paying for the Lambda invocations and API calls that occur during rotation.

For a single database password with automatic rotation, this might cost a few dollars a month. For an organization managing hundreds of secrets, the costs accumulate. If you don’t need automatic rotation, Parameter Store is the more economical choice.

A Practical Comparison Table#

To organize these distinctions, here’s how the services compare across key dimensions:

Automatic Rotation — Secrets Manager provides built-in support; Parameter Store requires custom orchestration.

Database Integration — Secrets Manager integrates natively with RDS, Aurora, Redshift, and DocumentDB; Parameter Store has no special integrations.

Cross-Account Sharing — Secrets Manager offers resource-based policies for cross-account access; Parameter Store relies on IAM and KMS policies.

Cost — Parameter Store is substantially cheaper for static configurations; Secrets Manager’s ongoing monthly charges become relevant when managing many secrets.

Simplicity — Parameter Store is simpler if you don’t need rotation; Secrets Manager is simpler if you do.

Use Case Fit — Secrets Manager excels for managed databases and credentials requiring rotation; Parameter Store excels for application configuration and static secrets.

Real-World Decision Framework#

So how do you actually choose? Start with this question: do you need automatic rotation?

If the answer is yes—especially for database credentials—Secrets Manager is your service. The built-in rotation logic eliminates complexity and reduces operational risk. The AWS-managed integrations with RDS and other databases make rotation seamless.

If the answer is no, ask the next question: are you sharing this secret across AWS accounts?

If you’re sharing across accounts and want a clean permission model, Secrets Manager’s resource policies are worth the extra cost. If you’re managing everything within a single account, Parameter Store’s per-call pricing might make more sense.

If you’re storing dozens of application configuration parameters alongside a few secrets, consider splitting them. Use Parameter Store for general configuration and Parameter Store’s SecureString type for static secrets, while using Secrets Manager for credentials that need rotation or cross-account access.

Practical Implementation Example#

Let’s walk through a concrete scenario. Suppose you’re building a multi-tier application that needs to store an RDS database password and several API keys for third-party services. You also need to rotate the database password monthly for compliance reasons, but the API keys are static and don’t require rotation.

With Secrets Manager, you’d store the RDS password as a secret with rotation enabled, leveraging the built-in RDS integration. With Parameter Store, you’d store the API keys as SecureString parameters—since they don’t rotate, Parameter Store’s simplicity and lower cost are appropriate.

To retrieve the RDS password in your application, you’d call the Secrets Manager API:

aws secretsmanager get-secret-value --secret-id prod/rds/password

This returns the current version of the secret, handling versioning transparently during rotation.

For the API keys, you’d call Parameter Store:

aws ssm get-parameter --name /app/api/stripe-key --with-decryption

Both services integrate with IAM, so your application’s execution role can be granted access only to the secrets and parameters it actually needs.

Encryption Key Management#

One nuance worth emphasizing: both services encrypt with KMS, but the key management implications differ. If you’re rotating credentials with Secrets Manager, you’re also managing key rotation—KMS keys should be rotated annually by default. This is true whether you use AWS-managed keys or customer-managed keys, though the operational burden is lighter with AWS-managed keys.

Parameter Store doesn’t add complexity here; the encryption key management is the same as with Secrets Manager.

Audit and Compliance#

Both services integrate with CloudTrail for audit logging. You can track who accessed which secrets or parameters, when those accesses occurred, and what operations were performed. For compliance-sensitive environments, these audit trails are essential.

Secrets Manager’s built-in rotation features create a particularly clean audit trail—you can see exactly when rotations occurred and whether they succeeded. If you’re building custom rotation logic with Parameter Store, you’re responsible for logging those events.

Making Your Final Decision#

The path forward depends on your specific requirements. If you’re managing database credentials and need automatic rotation, Secrets Manager is the right choice—the built-in integrations and purpose-built features justify the cost. If you’re storing application configuration and static secrets that don’t require rotation, Parameter Store is simpler and cheaper. If you need cross-account secret sharing, Secrets Manager’s resource policies make that cleaner.

Many organizations use both services in complementary ways. Secrets Manager for credentials requiring rotation, Parameter Store for configuration and static secrets. This isn’t either-or thinking; it’s choosing the right tool for each specific problem.

The key is understanding that these services solve slightly different problems. Secrets Manager is purpose-built for credential lifecycle management. Parameter Store is a general configuration tool that happens to support encryption. When you recognize that distinction, the choice becomes clear.