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Master Persons Index (MPI)

Overview and Terminology

The Master Persons Index (MPI) contains the golden record for a VA-affiliated individual (not always a veteran) and links their identity across systems. This system was formerly known as the Master Veteran Index (MVI).

  • In operations terms, the service is frequently referred to as PSM or PSIM (Person Services Identity Management)

  • PSM is in turn a child application of IAM.

  • Finally, while PSM refers to the identity database, accesses this information via VAAFI (VA Authentication Federation Infrastructure) which provides an authentication layer and SOAP API on top of PSM.

  • If a veteran is not found in the Master Persons Index, MPI makes a call to the DMDC (Defense Manpower Data Center) fallback DEERS (Defense Enrollment Eligibility Reporting System). DMDC is part of the DOD (Department of Defense)


Development Environment

The development environment ( integrates with the VA MPI iDev stack.

Staging Environment

The staging environment ( integrates with the VA MPI SQA stack.

Production Environment

The production environment ( integrates with the VA MPI Prod stack.


A downtime banner is displayed on the sign-in modal for any time Pagerduty has a status other than "active" for MPI. The vets-api application gets the status from PagerDuty every minute.


When MPI is unavailable, MHV premium users are unable to log in to,, and DS Logon users will not be able to access services which require verified user attributes, because we rely on MPI to tie the logged in user to their ICN (internal control number, the unique identifier used by MPI).

Errors and Monitoring

When MPI-related errors exceed the acceptable threshold, a Datadog monitor triggers an alert for further investigation.

Datadog also captures metrics related to the MPI service. Some of the key metrics are detailed below. You can reference a comprehensive list of available MPI metrics here.

  • vets_api.statsd.api_external_http_request_MVI_failed : The number of failed requests to MPI.

  • vets_api.statsd.api_external_http_request_MVI_success : The number of successful requests to MPI.

  • vets_api.statsd.api_external_http_request_MVI_time.avg : The average time per request to MPI.

  • vets_api.statsd.api_external_service_MVI_up : The current status of the MPI service, where a value of 1 indicates the service is available and 0 indicates the service is down.

To facilitate troubleshooting and error resolution, the vets-api integration with MPI emits logs prefixed with [MPI][Services].

Scheduled Down Times

Emails are sent to the MPI Stakeholders mailing group.

Escalation Procedure

Contact the OCTO-Identity team in the #VSP-Identity slack channel.


The OCTO-Identity team manages the MPI integration with

If you need urgent assistance due to a production issue outside of normal business hours, please send an email to During normal hours, you can seek assistance via the #VSP-Identity slack channel.

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