Parallel run pattern
The parallel run pattern operates existing and replacement systems on the same inputs while retaining one system’s authority and comparing their outputs.
First-Party Data Activation
An implementation approach in which legacy and replacement systems operate simultaneously for comparison, validation, or continuity.
- How it is used
- Supports brownfield lakehouse migration by keeping marketing activity running while teams validate the replacement against a legacy warehouse.
- How deep it goes
- Outlines planning, metric comparison, reconciliation, exit criteria, and decommissioning without specifying query-level implementation.
- Examples
- Uses an apparel retailer comparing warehouse and lakehouse queries for orders and cart value over weeks or months.
- What you can do after
- Practice/perform a controlled legacy-system off-ramp by reconciling outputs and retiring the old environment after validation.
Read how First-Party Data Activation explains parallel run pattern →
Architecture Modernization: Socio-technical alignment of software, strategy, and structure
The parallel run pattern is a migration pattern that runs legacy and replacement subsystems against the same input while using only one subsystem's output until the replacement is verified.
- How it is used
- Supports gradual subsystem migration when real-world verification and a fallback are more valuable than an immediate cutover.
- How deep it goes
- Explains the execution sequence from shared inputs through verification, output switching, fallback, and legacy decommissioning.
- Examples
- Uses Zalando’s returns extraction, new microservices, and endpoint-by-endpoint switching as its concrete example.
- What you can do after
- Operate/configure a staged migration with shared inputs, verified replacement outputs, controlled cutover, and a temporary fallback.
Related concepts
- brownfield environmentused by · A brownfield environment is an established technology landscape whose systems, infrastructure, data, processes, or dependencies must be retained, integrated, modernized, or changed.
- greenfield environmentcontrasts with · A greenfield environment is a development context for creating a new system without constraints imposed by an existing implementation or infrastructure.
- model comparisoncontrasts with · Model comparison is the systematic evaluation of two or more models under defined conditions and criteria to assess their relative performance or behavior.
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