Show HN: EloqDoc: MongoDB-compatible doc DB with object storage as first citizen

We're excited to share EloqDoc, a new open source document database built on top of Data Substrate. EloqDoc is designed around the principle of treating object storage (like S3) as a first-class citizen for durability and cost efficiency. If you love the flexibility of MongoDB's document model but are struggling with scaling, cost, and consistency due to its coupled architecture, EloqDoc is for you. It’s built to solve MongoDB's inherent infrastructure challenges while remaining fully compatible with existing MongoDB clients and drivers.

Key Features:

1. Object Storage as First Citizen: Uses object storage for primary durability, leveraging local NVMe caching to achieve both lower cost and higher performance than using block-level storage (e.g. EBS).

2. Decoupled Compute & Storage: Scale your compute/QPS independently of your storage capacity, or vice-versa, without data movement.

3. True ACID Transactions: Delivers full ACID compliance with especially fast distributed transactions—consistency without compromise.

4. Native Distribution & Multi-Writer: It's a natively distributed database, eliminating complex manual sharding routers (like mongos) and supporting true Multi-Writer scalability.

Check it out: https://www.github.com/eloqdata/eloqdoc

We welcome any feedback, critique, or questions on the EloqDoc!

Show HN: EloqDoc: MongoDB-compatible doc DB with object storage as first citizen
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Mongo Atlas also supports using archive database to store infrequently accessed cold data. It’s also object storage based.

Typically a separate archive database is not desired choice. You need to specify the rule how old the data is move from production database to archive database. Also the archive database is read only and slow, you can not achieve transaction between production database and archive database.

That’s correct. FerretDB and DocumentDB both pursue PostgreSQL-based document models.

EloqDoc follows a fundamentally different architectural path. Instead of executing in Postgres, we leverage the existing MongoDB parser and executor to ensure maximum compatibility. Our main contribution is to replace the single-writer WiredTiger storage engine entirely with Data Substrate.

The Data Substrate is an abstract layer built specifically to handle distributed database fundamentals: scalable buffer pooling, concurrency control, durability, elasticity, and fault tolerance. You can read more: https://www.eloqdata.com/blog/2025/07/14/technology

This architectural choice is what enables EloqDoc to deliver features that Postgres-based solutions cannot easily match, including: full compatibility, native Multi-Writer capability, Object Storage First and extremely low-latency distributed transactions.

That is right. We leverage some of the AGPL MongoDB code for the parser, as indicated by the License. Our own code can be licensed differently, see a previous discussion on Hacker News [1]. The Mongo API are reasonably stable over the last few years, only seeing very minor changes. Most of the later versions improved upon performance and transactions, which we support natively with our underlying technologies. Still, if you have any specific API that you feel is needed, we'd be happy to implement and we welcome community contributions.

[1] https://news.ycombinator.com/item?id=44937978