Vault Agent is a client daemon that provides the following features:
Auto-Auth - Automatically authenticate to Vault and manage the token renewal process for locally-retrieved dynamic secrets.
API Proxy - Allows Vault Agent to act as a proxy for Vault's API, optionally using (or forcing the use of) the Auto-Auth token.
Caching - Allows client-side caching of responses containing newly created tokens and responses containing leased secrets generated off of these newly created tokens. The agent also manages the renewals of the cached tokens and leases.
Templating - Allows rendering of user-supplied templates by Vault Agent, using the token generated by the Auto-Auth step.
Process Supervisor Mode - Runs a child process with Vault secrets injected as environment variables.
One of the benefits of using the Vault Agent is that it will manage the lifecycle of cached tokens and leases automatically. This means that the agent will handle the token renewal and revocation logic, as well as the lease renewal and revocation logic for the secrets that are cached by the agent. This reduces the burden on the application developers and operators, and ensures that the tokens and secrets are always valid and up-to-date. Reference: Vault Agent | Vault | HashiCorp Developer, Caching - Vault Agent | Vault | HashiCorp Developer