AWS Systems Manager Parameter Store
AWS hierarchical key-value store for configuration data and secrets with free standard tier, KMS encryption for SecureString parameters, and IAM access control.
Score Breakdown
⚙ Agent Friendliness
🔒 Security
Path-based IAM policies enable fine-grained access. SecureString uses KMS — must grant kms:Decrypt permission separately. CloudTrail audit trail available.
⚡ Reliability
Best When
Storing non-rotating configuration and low-security secrets in AWS where cost matters — free standard tier beats Secrets Manager pricing for simple config.
Avoid When
You need automatic rotation, cross-account secret sharing, or detailed rotation audit logs — use Secrets Manager instead.
Use Cases
- • Storing and retrieving agent configuration values (feature flags, endpoints, thresholds) with hierarchy
- • Storing encrypted secrets as SecureString parameters as a cheaper alternative to Secrets Manager
- • Environment-specific configuration using hierarchical paths (e.g., /prod/agent/api-key vs /dev/)
- • Sharing configuration across EC2/Lambda/ECS agents without code changes via SDK retrieval
- • Change notifications via EventBridge when parameter values are updated by operators
Not For
- • Automatic secret rotation (use Secrets Manager for credentials needing rotation)
- • Very frequent reads without caching — Standard tier is free but Advanced tier charges per API call
- • Non-AWS workloads (use Vault, Doppler, or cloud-native alternatives)
Interface
Authentication
AWS IAM with resource-based policies on parameter hierarchy paths. ssm:GetParameter, ssm:GetParametersByPath with path prefix conditions. Instance Profile recommended.
Pricing
Standard tier is free — excellent for most use cases. Advanced adds parameter size limits increase (8KB vs 4KB) and TTL.
Agent Metadata
Known Gotchas
- ⚠ GetParametersByPath has 40 TPS limit on Standard tier — paginated bulk reads can throttle agents
- ⚠ SecureString requires KMS key permission in ADDITION to SSM permission — double IAM check required
- ⚠ Parameter names are case-sensitive — /prod/API-Key and /prod/api-key are different parameters
- ⚠ Standard parameters: 4096 byte value limit; Advanced: 8192 — plan for JSON-encoded configs
- ⚠ Parameter history keeps last 100 versions — GetParameterHistory useful for change auditing in agents
Alternatives
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Scores are editorial opinions as of 2026-03-07.