Data migration case study: Legacy to modern,
at billion-row scale.
An end-to-end migration for an enterprise client: moving years of operational and financial data out of a legacy stack and into a new PostgreSQL and MongoDB platform, strictly according to approved field mappings.
Lane 1 · Relational migration
Lane 2 · Daily document ingestion
The challenge
Financial records lived in Zoho Books, while CRM, CMS, seller and order data sat in separate legacy sources. The target schemas were different, the volumes enormous and the cutover window short.
The approach
Zoho Books data was exported to S3, then pulled and transformed according to a field-level mapping and loaded into PostgreSQL. CRM-scale tables were processed in chunks with pandas and multiprocessing to use every core.
The result
Billions of CRM records plus CMS, seller and OMS data now live in the new platform, while a daily job loads S3 call logs and audit files into MongoDB so history keeps flowing.