MongoDB
MongoDB is built and commercially stewarded by MongoDB Inc. (NASDAQ: MDB). Server 8.0, GA'd October 2024, is the current long-term-support line (supported through October 2029); 8.3 is the newest quarterly rapid release as of mid-2026. Community Server has shipped under the Server Side Public License (SSPL) since October 2018 — not OSI-approved, and it forces anyone offering MongoDB as a hosted service to open-source their entire management stack. AWS's response was DocumentDB: a separately engineered, MongoDB-API-compatible database built on Amazon's own Aurora storage engine, not a MongoDB fork — it shares no MongoDB source code, which is exactly how it sidesteps SSPL's terms. Documents are stored as BSON on the WiredTiger storage engine, with multi-document ACID transactions available since 4.0 (2018). DB-Engines ranks it #5 overall (score ~379-384, early 2026) and #1 among document stores, with over 66,400 Atlas customers reported as of April 2026 (fiscal Q1 2027). Current version/status: Server 8.0 (LTS, GA October 2024, supported through October 2029); 8.3 is the latest quarterly rapid release as of mid-2026. License: Server Side Public License (SSPL) since Oct 2018 for Community Server — not OSI-approved; Enterprise Advanced is separately, commercially licensed. Pricing: Atlas cloud: free M0 tier forever (512MB, up to ~100 ops/sec); Flex tier $8-$30/mo; Dedicated cluster
Pick MongoDB when your schema is genuinely fluid and write throughput beats joins — event logs, content catalogs, mobile app backends storing nested JSON. Skip it for anything transactional-first: ledgers, inventory, multi-entity bookings — reach for PostgreSQL instead, whose decades-old ACID guarantees and query planner outclass MongoDB's bolted-on transactions (added in 4.0, 2018, and carrying a real but not precisely benchmarked write-performance overhead versus non-transactional writes). The honest weakness the community itself flags: SSPL isn't OSI-approved open source, and MongoDB rewrote its license in 2018 specifically to stop cloud vendors from reselling MongoDB-as-a-service without contributing back. AWS's DocumentDB — launched three months after SSPL, not before it — sidesteps the license entirely by not using any MongoDB code at all; it's API-compatible, not a fork. Known weakness: SSPL is not OSI-approved, blocking inclusion in Fedora/Debian, and it's the reason AWS's DocumentDB is a separately-built, MongoDB-API-compatible service rather than a hosted vanilla MongoDB (DocumentDB shares no MongoDB code — it's not a fork); multi-document ACID transactions (since 4.0, 20
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