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matharmin

1,673 karma · joined October 2, 2015

Co-founder at JourneyApps, currently focusing on PowerSync.

https://powersync.com

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matharmin··on Firebase SDK is CRASHING ALLLL iOS Apps, since today morning
While Firebase has support for queries with realtime updates and offline caching, I wouldn't quite call it offline sync.
matharmin··on Show HN: Prove your code produced your claims without making reviewers rerun it
The readme has a lot of words but still does not clearly explain what this does or what you'd use it for.

The best I can gather is that this captures telemetry while you're running some computationally-expensive job, and checks that the resource usage roughly matches what it's supposed to be. But what does "Tamper-evident" mean? I assume you sign with your own private key? What exactly prevents the data from being faked?

matharmin··on Stacked PRs are now live on GitHub
I've been using the preview for a bit, and I'm quite surprised to see them expanding the preview with so many unfixed issue.

For example, merging an entire stack is completely broken in many cases: https://github.com/github/gh-stack/discussions/212

You can merge one by one, but if you're using squash and merge, you need a re-approval for each PR in the stack if you require reviews. This makes you lose out on arguably the biggest gain of stacked PRs.

The command line tooling (gh stack) helps to make things slightly less manual, but you still need to be very aware of how git rebase works, the tooling just helps automate it across multiple branches. For example, just running the "gh stack rebase" commands that the UI suggests won't work if your local branches are not in sync with the remote ones, and the tooling won't point that out to you.

I do find the stack UI quite nice. It's quite minimal compared to standalone PRs, but it's enough to show the relationship between them.

(My comments all assume you already have a good reason to stack PRs. This tooling just help to make the workflow easier, it does not give any new capabilities)

matharmin··on Paging Through a Parquet File in DuckDB: File_row_number or Offset?
I'd assume it's common knowledge that you cannot paginate using OFFSET + LIMIT unless you use ORDER BY on an unique set of columns, no matter what database you're using. The only exception is when the database provides an explicit order guarantee without the ORDER BY, such as the case with `preserve_insertion_order = true` here.
matharmin··on DMARC has been public since 2012 but most company domains still don't enforce it
I never understood the point of the anti-virus adding a message to _outgoing_ emails. Basically "I swear there is no virus in this email I'm sending you, trust me bro".
matharmin··on DMARC has been public since 2012 but most company domains still don't enforce it
I'm not familiar with Outlook's resending, but the use case is supported if the sender uses DKIM. If the email is forwarded without changing any details, it can keep the DKIM signature. That allows the forwarded email to still pass DMARC.

Now if the sender used SPF + DMARC but not DKIM, this does not work, since the sender IP can't be verified with the forwarded email. In that case, the forwarder has to change the from address to prevent the email from failing DMARC and be rejected.

In practice, senders using SPF+DMARC but not DKIM should be quite rare, you see DKIM+DMARC much more often.

matharmin··on DMARC has been public since 2012 but most company domains still don't enforce it
There are lots of free tools that automatically analyze the reports for you (you send it to them, instead of yourself).

But if you send all emails for your domain from one email server, you could just disable rua reporting. The reports are mainly useful to see whether you have some misconfigired email server somewhere that causes (or will cause) dropped emails. That can easily happen if you send some email from your own server, some via sendgrid, some via some marketing tool, and start to lose track of them. But for a personal email server, that's not common.

matharmin··on New HIV vaccine shows unprecedented success in preclinical study
That PrEP is in some ways similar to a vaccine, and there is still a lot of value in getting a better vaccine (cheaper and/or lasting longer).
matharmin··on Do you really need separate systems when you already have Postgres?
Why would anyone use GridFS for any serious use case? It costs 10-20x as much as storing the files on S3. If unless you already have all your data in MongoDB and don't want an additional dependency for a small number of files it makes sense, but it definitely is not a case for using MongoDB by itself.
matharmin··on Codex logging bug may write TBs to local SSDs
LLMs do learn from mistakes. Not as directly from individual mistakes like humans do, but in aggregate the models have improved much more in the last year than most humans I know learn in the same time.
matharmin··on Deno Desktop
Do you mean "Unlike Deno Desktop"? Deno Desktop definitely relies on a browser engine.
matharmin··on Let's Encrypt bans certificate usage in any US sanctioned territory [pdf]
Yeah, they don't make it that clear, but you get basically the same functionality as with LetsEncrypt for free, including wildcard certs. You basically only need to pay for manually issued certs, or some of their other additional features.
matharmin··on Let's Encrypt bans certificate usage in any US sanctioned territory [pdf]
I use them in some cases to avoid the rate limits on LetsEncrypt, and they have better support for some older platforms (like ancient Android versions), and I'm pretty happy so far. I have a paid account to support them, but it's not a requirement for ACME certs. It works without issue with Kubernetes Certbot, and seamless to switch between ZeroSSL and LetsEncrypt.

I can't comment on the EU part though - not that relevant in my case.

matharmin··on How's Linear so fast? A technical breakdown
At PowerSync we use a wa-sqlite build with SQLite3MultipleCiphers for encryption at rest.

You do still need a secure key to use with this. The simplest is to persist the key server-side (and specifically not on the client), and provide it to the JS after signing in. If you need to support a completely offline PWA you need something else, e.g. prompting the user for a passcode each load.

matharmin··on Cloudflare to cut about 20% of its workforce
Now you can ask "Is it easier to ask an AI agent to do X than asking my employee?"

Good metrics is difficult, but sometimes a simple comparison like that is enough.

matharmin··on Linux 7.0 Broke PostgreSQL: The Preemption Regression Explained
Yup - interesting to see so much written about Postgres having a performance regression on Linux 7.0, in a scenario that affects almost no-one in practice. Meanwhile MongoDB refuses to run at all on Linux 7.0 due to some issue with tcmalloc.

https://jira.mongodb.org/browse/SERVER-121885

matharmin··on An update on GitHub availability
In many of my projects don't show any closed pull requests for the last 6 days. The CLI can list them, but anything going through search shows nothing.

Their support acknowledged the issue, but has been silent since then, and the status page still shows nothing other than the potentially-related issue on the 27th. It looks like it has been resolved on some repositories in the meantime, but I still have the issue across multiple orgs and repositories.

https://github.com/orgs/community/discussions/193388

matharmin··on GitHub Stacked PRs
This is not just about the UI, it's about the mental model and management of the changes.

Just covering the review process:

Yes, you can structure your PR into 3 commits to be reviewed separately. I occasionally structure my PRs like this - it does help in some cases. But if those separate parts are large, you really want more structure around it than just a commit.

For example, let's say you have parts A, B and C, with B depending on A, and C depending on B.

1. I may want to open a PR for A while still working on B. Someone may review A soon, in which case I can merge immediately. Or perhaps it will only be reviewed after I finished C, in which case I'll use a stacked PR. 2. The PR(s) may need follow up changes after initial review. By using stacked PRs instead of just separate commits, I can add more commits to the individual PRs. That makes it clear what parts those commits are relevant to, and makes it easy to re-review the individual parts with updated changes. Separate commits don't give you that.

Stacked PRs is not a workflow I'd use often, but there are cases where it's a valuable tool.

Then apart from the review process, there are lots of advantages to keeping changes small. Typically, the larger a change, the longer it lives in a separate branch. That gives more time for merge conflicts to build up. That gives more time for underlying assumptions to change. That makes it more difficult to keep a mental map of all the changes that will be merged.

There are also advantages to deploying small changes at a time, that I won't go into here. But the parent's process of potentially merging and deploying the search index first makes a lot of sense. The extra overhead of managing the index while it's "unused" for a couple of days is not going to hurt you. It allows early testing of the index maintenance in production, seeing the performance overhead and other effects. If there's an issue, it's easy to revert without affecting users.

The overall point is that as features become large, the entire lifecycle becomes easier to manage if you can split it into smaller parts. Sometimes the smaller parts may be user-visible, sometimes not. For features developed in a day or two, there's no need to split it further. But if it will span multiple weeks, in a project with many other developers working on, then splitting into smaller changes helps a lot.

Stacked PRs is not some magical solution here, but it is one tool that helps manage this.

matharmin··on RubyGems Fracture Incident Report
I can see a lot of time was put into the report, and it helps to have the detail, but in my mind it glosses over one of the most important parts: The dispute in the stewardship of the bundler and rubygems open-source projects.

As I understand it, Ruby Central controlled the rubygems and bundler github organizations, but did not "own" the projects in the traditional sense - the individual contributers have copyright on the code, and potentially even trademark rights. By then removing access of core maintainers to those projects, they removed access to something they don't "own" themselves.

This is all complicated by the fact that controlling a github organization or repo is different from owning the trademark or copyright. But some of the original maintainers clearly felt they had more of a right to those projects than Ruby Central did.

I believe not clarifying this before making these access changes was the biggest mistake that Ruby Central made, and it's not even mentioned in this report.

matharmin··on Anthropic, please make a new Slack
What features are you using that the $18/user/month plan doesn't cover?
matharmin··on Resizing windows on macOS Tahoe – the saga continues
In my experience, Windows is very far from a "it just works" OS.
matharmin··on Fast Properties in V8 (2017)
This is still an interesting read, but has anything here changed in the meantime? And out of interest, do other JS engines use the same type of structure to represent properties?
matharmin··on How to Build Reactive Declarative UI in Vanilla JavaScript
There are a bunch of utilities that don't actually _do_ anything useful. The proxy in this example is used for nothing other than debug logs. The DOM utility layer just slightly reduces the number of LOC to create a DOM node.

And then you end up with consumer code that is not actually declarative? The final code still directly manipulates the DOM. And this shows the simplest possible example - creating and removing nodes. The difficult part that libraries/frameworks solve is _updating_ the DOM at scale.

matharmin··on Fifty problems with standard web APIs in 2025
If that is your source, then Safari was _way_ behind for all of 2025 up until this month, where it suddenly caught up.
matharmin··on Could lockfiles just be SBOMs?
Superset of dependencies, but often a subset of info per depedency.
matharmin··on Could lockfiles just be SBOMs?
SBOM may contain similar info to lockfiles, but the purposes are entirely different.

Lockfiles tells the package manager what to install. SBOM tells the user what your _built_ project contains. In some cases it could be the same, but in most cases it's not.

It's more complicated than just annotating which dependencies are development versus production dependencies. You may be installing dependencies, but not actually use them in the build (for example optional transitive dependencies). Some build tools can detect this and omit them from the SBOM, but you can't omit these from your lockfile.

Fundamentally, lockfiles are an input to your developement setup process, while SBOM is an output of the build process.

Now, there is still an argument that you can use the same _format_ for both. But there are no significant advantages to that: The SBOM is more verbose, does not diff will, will result in worse performance.

matharmin··on 100k TPS over a billion rows: the unreasonable effectiveness of SQLite
As mentioned in those threads, there is no SQLite WAL corruption if you have a working disk & file system. If you don't, then all bets are off - SQLite doesn't protect you against that, and most other databases won't either. And nested transactions (SAVEPOINT) won't have have any impact on this - all it does in this form is reduce the number of transactions you have.
matharmin··on Listen to Database Changes Through the Postgres WAL
We're relying on logical replication heavily for PowerSync, and I've found it is a great tool, but it is also very low-level and under-documented. This article gives a great overview - I wish I had this when we started with our implementation.

Some examples of difficulties we've ran into: 1. LSNs for transactions (commits) are strictly increasing, but not for individual operations across transactions. You may not pick this up during basic testing, but it starts showing up when you have concurrent transactions. 2. You cannot resume logical replication in the middle of a transaction (you have to restart the transaction), which becomes relevant when you have large transactions. 3. In most cases, replication slots cannot be preserved when upgrading Postgres major versions. 4. When you have multiple Postgres clusters in a HA setup, you _can_ use logical replication, but it becomes more tricky (better in recent Postgres versions, but you're still responsible for making sure the slots are synced). 5. Replication slots can break in many different ways, and there's no good way to know all the possible failure modes until you've run into them. Especially fun when your server ran out of disk space at some point. It's a little better with Postgres 17+ exposing wal_status and invalidation_reason on pg_replication_slots. 6. You need to make sure to acknowledge keepalive messages and not only data messages, otherwise the WAL can keep growing indefinitely when you don't have incoming changes (depending on the hosting provider). 7. Common drivers often either don't implement the replication protocol at all, or attempt to abstract away low-level details that you actually need. Here it's great that the article actually explains the low-level protocol details.

matharmin··on Context engineering is sleeping on the humble hyperlink
Probably a security feature. If it can access the internet, it can send your private data to the internet. Of course, if you allow it to run arbitrary commands it can do the same.
matharmin··on Show HN: EloqDoc: MongoDB-compatible doc DB with object storage as first citizen
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.
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