Running an application across two physical databases is not a straightforward thing. One of the relatively easier ways to do it involves assigning each database instance a shard number and then arranging for all your primary key IDs to end with that number. For example, shard 0 generates IDs like 1230, 40, 482340, shard 1 generates IDs like 1231, 41, 482341, and shard 2 generates IDs like 1232, 42, 482342, etc. all the way up to 9. If you want more than 10 database shards, it gets more involved.

My brain is wired oddly, so I came to wonder how you would quickly get the shard ID for an ID (e.g. shard 1 for 1231). This is really easy with decimal math; you just divide by 10. However, we run our databases on computers that can only do binary math, so its not actually simple.

But it turns out you can do it quite fast! There’s one weird number, expressed as `0x1999999A` hexadecimal, that is very close to multiplying by the fraction 1/10 (plus further binary math and register trickery). Thus you can do this in only a few instructions on Intel processors released in the past twenty years.

I’m really glad someone else figured this out.

Is it too late to do hottakes for something that’s been around for nearly a decade?

OAuth2 pros:

• I can allow other sites to use my data with some confidence that, at least, my authentication information won’t leak
• It has made really cool stuff possible at my current workplace and workplace-2
• Libraries to make it happen in server-side apps are pretty good

Cons:

• There are a bajillionty implementations and standard definitions of OAuth2 (for somewhat justifiable reasons)
• If you want to tinker with an OAuth2 API, you’re in a bit of hurt because you can’t just grab a token and start playing (mostly, depending on the implementer)
• Those open source libraries are the kind of thing that drive maintainers away pretty quickly 😬

Overall: would not uninvent this technology.

There’s a moment of despair when extracting functionality from a larger library, framework, or program. The idea grows, a seed at first and then a full-blown tree, that the coupling in this functionality isn’t all bad. A lot of people talk only about coupling and leave out cohesion. They aren’t mutually exclusive! When the two are balanced, it’s hard to come up with a reason to start extracting.

On the other hand, sometimes that moment of despair strikes when you start really digging into the domain and realize this chunk of functionality isn’t what you thought it was. Maybe it’s not coherent (see above!) or perhaps the model of the domain isn’t deep enough. This is a pretty good signal to hit the brakes on the refactoring, figure the domain out, and reconsider the course of action.

Feature envy rears its head in extractions too. Patterns of crosstalk between the existing thing and the new thing are a sure sign of feature envy. It’s tempting to say, hey maybe you really need a third thing in the middle. That’s probably making matters worse though.

That said, changing bidirectional communication to unidirectional is usually a positive thing. Same for replacing any kind of asynchronous communication with synchronous. Or replacing lockstep coordination with asynchronous messaging. Envy is tricky!

(I) often encourage starting a new service or application within your existing “mothership”. The trendy way to say this right now is “monorepo all the things” or build a “modular monolith”. I find this compelling because you can leverage a lot of existing effort into operationalizing, tooling, and infrastructure. Once you know the domain and technical concerns specific to the new thing, you can easily extract into its own thing if you need to. The other edge of a monorepolith is that path dependence is a hell of a thing. Today is almost certainly an easier day to split stuff out than tomorrow.

A thing to consider pursuing is a backend-for-frontend service in pursuit of a specific frontend. It doesn’t even have to serve an application. You may have services that are specific to mobile, desktop, apps, APIs, integrations, etc. Each of these may need drastically different rates of change, technical features, and team sets.

Probably don’t split out a service so that a bunch of specialized people can build a “center of excellence” for the rest of the organization to rely upon. This is a very fancy way to say “we are too cool for everyone else and we just can’t stand the work everyone else is doing”. On their best day, the Excellence team will be overwhelmed by the volume of work they have put in front of themselves to make Everything Good. On their worst day, they will straight give up.

If you split something out, realize you’re going to have to maintain it until you replace it. And you’re going to rebuild the airplane while it’s flying. If you’re not really into that, stop now. Just because you can’t stand Rails, relational databases, or whatever doesn’t mean you should jump into an extraction.

A few months ago I wrote about Framework and Library people. I had great follow-up conversations with Ben Hamill, Brad Fults, and Nathan Ladd about it. Some ideas from those conversations:

• use a well-worn framework when it addresses your technical complexities (e.g. expose functionality via the web or build a 3-d game) and your domain complexity (e.g. shopping, social networking, or multi-dimensional bowling) is your paramount concern

• once you have some time/experience in your problem domain, start rounding off corners to leave future teammates a metaframework that reduces decision/design burdens and gives them some kind of golden path

• frameworks may end up less useful as integration surface area increases

• napkin math makes it hard to justify not using a framework; you have to build the thing and accept the cost of not having a community to support you and hire from

• to paraphrase Sandi Metz on the wrong abstraction: “(Using) no abstraction is better than the wrong abstraction”; if you’ve had a bad time with a framework, chances it was an inappropriate abstraction or you used the abstraction incorrectly