T4 – a versioned datastore with branching and time-travel (S3-backed)
Hi HN, I built t4, a datastore that stores its WAL and snapshots in S3. Instead of traditional storage, it writes append-only segments to object storage and reconstructs state from checkpoints + WAL. A side effect of this model is that the database becomes naturally versioned: you can restore any past state, branch from any point (with copy-on-write) and replay history I started this as an experiment to replace etcd in Kubernetes, but it’s evolving into a general-purpose versioned state store. Curious what people think about it and appreciate any feedback!
Does a similar job
all alternatives →
- CSCallFS – S3-style object store in one Go binary (MIT)2025 · github.com · ▲66
We started CallFS after yet another late-night “why did the uploads vanish?” incident. Our small team had stitched together rsync, a fragile NFS mount, and an S3 bucket—none of it observable, all of it waiting to bite us. So we wrote a single-process file service in Go that: • Speaks the S3 API (so existing tooling works). • Stores hot data on local disks for speed; cold data can sit in any S3-compatible bucket. • Exposes Prometheus metrics and JSON logs by default, because “what happened?” shouldn’t be guesswork. • Ships as a ~25 MB static binary—no external deps, MIT license. Today it’s…
- SVSirixDB – versioning through efficient snapshotting2018 · ▲55
I've already posted yesterday, but I'd really love to get comments, any kind of questions, suggestions and help would be greatly appreciated as it's an Open Source project of mine (and was for others during my studies at the University of Konstanz 6 years ago). Since then I spent countless ours to bring forth the idea of a versioned storage system, especially well suited for analytical tasks for timd-varying data. Especially I'd love to discuss what documentation you need, which next steps are necessary (JSON, Cloud...), API additions or changes... I've updated the README quiet a bit, such…
- WSWe scaled Git to support 1 TB repos2022 · xethub.com · ▲279
I’ve been in the MLOps space for ~10 years, and data is still the hardest unsolved open problem. Code is versioned using Git, data is stored somewhere else, and context often lives in a 3rd location like Slack or GDocs. This is why we built XetHub, a platform that enables teams to treat data like code, using Git. Unlike Git LFS, we don’t just store the files. We use content-defined chunking and Merkle Trees to dedupe against everything in history. This allows small changes in large files to be stored compactly. Read more here:…
- LCLow-cost backup to S3 Glacier Deep Archive2022 · github.com · ▲120
Hi, most people (hopefully) have local backups. However, when that backup fails, it is good to have a backup stored somewhere off-site. In the old days you would ship physical drives/tapes, which is cumbersome, costly, and slow. With fast upload speeds, it is now possible to upload your data to the cloud. I have found S3 Glacier Deep Archive to be a great solution for this: - It is very cheap ($1/TB/month for US region) - Very reliable (99.999999999% data durability, data spread over 3 Availability Zones) However, usability out of the box is not that great, I'm not aware of…
- SSSirixDB – Storing and Querying of Temporal Data (Java and Open Source)2018 · ▲13
I'm developing a storage system for versioning data at the subfile level, especially well suited for SSDs due to its log-structured COW nature. It implements a novel versioning algorithm called sliding snapshot, a diff-algorithm which makes use of our stable record-identifiers and optionally hashes, another diff algorithm for importing similar XML-documents as a versioned resource as well as novel XPath axis to navigate not only in space, but also in time. Recently, I've implemented a higher level, asynchronous REST-API with Kotlin (Coroutines) and Vert.x in a seperate module. The system is…
More dev tools this month
the category →



OpenTrailPaper is open-source bike computer firmware for the LilyGO T5S3 4.7" E-Paper PRO. It supports offline maps, GPX routes, FIT recording and Bluetooth sensors.
Dev tools · 2d ago · opentrailpaper.com

Open-source GTM skills for technical founders
Dev tools · 30d ago · gtmcofounder.com

Launched alongside, April 2026
the whole month →
- AG
Thought the resources for GPU arch were lacking, so here we are
Life & fun · Apr 2026 · jaso1024.com
- IB
Built a ~9M param LLM from scratch to understand how they actually work. Vanilla transformer, 60K synthetic conversations, ~130 lines of PyTorch. Trains in 5 min on a free Colab T4. The fish thinks the meaning of life is food. Fork it and swap the personality for your own character.
AI · Apr 2026 · github.com

- BC
Life & fun · Apr 2026 · sam-burns.com
- IB
With social media and now AI, its important to keep the indie web alive. There are many people who write frequently. Blogosphere tries to highlight them by fetching the recent posts from personal blogs across many categories. There are two versions: Minimal (HN-inspired, fast, static): https://text.blogosphere.app/ Non-minimal: https://blogosphere.app/ If you don't find your blog (or your favorite ones), please add them. I will review and approve it.
AI · Apr 2026 · text.blogosphere.app