We Migrated from MongoDB 7.0 to PostgreSQL 17: Handling 1B+ Documents

Why We Migrated

Our team maintains a large-scale social media analytics platform ingesting over 50M user activity events daily, totaling 1.2B documents stored in a sharded MongoDB 7.0 cluster. While MongoDB served us well for high-throughput writes and flexible schema needs early on, we hit critical limitations as our workload evolved:

Complex cross-collection aggregations for billing and user attribution took 10+ seconds, impacting customer dashboards.

Lack of native ACID transactions across shards led to data inconsistencies in billing workflows.

Relational metadata (user profiles, subscription tiers) stored in separate collections required slow application-side joins.

PostgreSQL 17’s upcoming features, including enhanced JSONB performance, declarative partitioning improvements, and MERGE statement optimizations, aligned with our long-term roadmap.

Pre-Migration Assessment

We started with a 3-month audit of our MongoDB…