What is a Parallel Run?

A migration strategy where the legacy platform and replacement platform operate simultaneously. Used to validate the new system before decommissioning the old one, but the dual-platform period carries costs that migration budgets frequently underestimate.

In IT, a parallel run is a validation exercise. Run both systems on the same inputs, compare the outputs, confirm the new system works correctly, then cut over. Clean, methodical, time-boxed.

In martech, a parallel run is that plus an operational burden that migration plans routinely undercount. For the duration of the parallel period, two platforms need licensing, two systems need maintenance, two sets of integrations need monitoring, and the team splits its attention between operating the current environment and building the future one.

Where the budget math breaks

A vendor offering a free year on a new platform often calculates the customer’s cost of switching as the new license fee. The parallel run reveals the actual number. During the overlap period, the organization is paying for the legacy platform (which cannot be decommissioned until migration is complete), the new platform (even if the first year is free, implementation costs are not), and the people who have to keep both running.

Content migration, data synchronization between systems, and integration rewiring all happen during this window. If any of those workstreams fall behind schedule, the parallel run extends, and the costs compound.

Planning for the real timeline

Effective migration planning treats the parallel run as its own budget line, not as a footnote. It includes dual licensing costs, the operational overhead of maintaining two systems, the productivity loss from a team working across both environments, and a contingency for schedule extension. Organizations that plan for a 3-month parallel run and budget for 6 rarely regret the margin.

Frequently Asked Questions

How long does a parallel run typically last?

It depends on the platform complexity, but 3 to 6 months is common for martech migrations. The risk is that parallel runs extend. Integration issues, data reconciliation problems, and team bandwidth constraints push the cutover date further out, and every month of extension means another month of dual-platform costs.

Can you avoid a parallel run entirely?

Some organizations attempt a hard cutover: turn off the old system, turn on the new one. This eliminates dual-platform costs but introduces significant risk if the new system has gaps. Most enterprise martech migrations opt for some form of parallel operation because the cost of downtime or data loss outweighs the cost of running both systems temporarily.

Related Definitions

  • Rip and Replace — The strategy of completely removing an existing technology platform and replacing it with a new one in a single migration, rather than running both systems in parallel or migrating incrementally.
  • Switching Costs — The total financial, operational, and organizational costs an organization incurs when replacing one technology vendor or platform with another.
  • Total Cost of Ownership (TCO) — The comprehensive financial estimate of all direct and indirect costs associated with purchasing, implementing, operating, and eventually replacing a technology platform over its full lifecycle.
  • Content Estate — The total inventory of content assets an organization owns and maintains across its digital platforms. The term carries weight because it frames content as a managed asset portfolio, not a folder of files.