Case study

Event store and audit trail

Qfact needed to be able to prove what its platform had done. We worked with the software architect to build a new event store for business logic persistence, using event sourcing to make every change in system state accountable.

Client Qfact
Sector B2B SaaS and analytics
Period 2018 to 2024
The challenge

Why this needed doing

Existing data had to migrate into the new store accurately. An audit trail that starts with a bad migration is worse than no audit trail at all.

The store then had to be integrated into a platform that was already serving thousands of daily users, with no disruption to operations or uptime.

What we delivered

  • The event store designed together with the software architect, for scale and for reliable replay.
  • Implementation and testing of the store itself, with Cassandra for event storage and MongoDB for read model tracking.
  • Migration of existing data and integration into the running platform, delivered through SCRUM.
  • Audit capability meeting government compliance requirements, with exact visibility into what changed on any model, when, and what caused it.

The result

Compliance reporting stopped being an investigation and debugging got dramatically simpler, because the platform could now answer what happened and why for any record it holds.

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