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Show HN: EloqDoc: MongoDB-compatible doc DB with object storage as first citizen (github.com)

46 points by iamlintaoz ↗ HN
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!

9 comments

[ 2.8 ms ] story [ 34.8 ms ] thread
the_precipitate
FerretDB and DocumentDB seem to be the only other two Mongo-compatible open source database implementations. Both are based on PostgreSQL.
matharmin
FoundationDB also has a Mongo-compatible document layer, but it seems like the last release was 6 years ago, so probably doesn't count anymore.
PeterZaitsev
I see the license is AGPLv3 while current MongoDB versions as SSPL - does it means you took the MongoDB Parser circa 2018 as a base ?
freakynit
Nice one..

Btw, your login/signup page auth is broken. Isn't moving ahead after google auth. Fyi, I use firefox in strict privacy mode.

iamlintaoz
For full transparency, I am the CEO of EloqData and I am happy to answer any questions you have. EloqDoc has been open-sourced for awhile, and we are glad to announce that the current code is stable for you to test on your workload.
matharmin
The project looks great! Object storage is often so much better in terms of cost efficiency than a database on EBS. It's often 10-20x more expensive for EBS after taking into account that you need 3x replicas for a typical MongoDB deployment, and need to over-provision the storage. And being able to scale compute independently from storage is great.

The biggest things I'm missing from the docs (checked the github page and the site) is seeing what MongoDB features are supported or not. I've worked with Azure CosmosDB before, and even though it claims MongoDB compatibility, it has many compatibility issues as soon as you have more than a basic CRUD application. Some examples include proper ChangeStream support, partial index support, multi-key index support, set of supported aggregation pipeline operations, tailable cursor support, snapshot queries.

Another thing that's not clear: What does multi-master/multi-write mean in practice? What happens if you write to the same data at the same time on different nodes?

akshayshah
Very cool! Using “object storage for primary durability” seems difficult for any OLTP workload that’s latency-sensitive - there’s a fundamental tradeoff between larger batch sizes to control write costs and smaller batches to reduce latency. This hurts OLTP workloads especially badly because applications often make multiple small writes to serve a single user-facing request. How does EloqKV navigate this tradeoff?

Also, I’d love to see:

- A benchmark that digs into latency, throughput, and cost for a single workload. Most of the benchmarks I saw are throughput-only.

- Some explanation of the “patented 1PC protocol.” Your website [1] suggests that you treat single EBS volumes as high-durability, replicated storage, which seems unusual to me - apart from io2 volumes, EBS is designed for less than 3 nines of durability [2].

[1]: http://www.eloqdata.com/blog/2025/07/15/data-substrate-detai...

[2]: https://aws.amazon.com/ebs/features/