Apple's Swift Powers the New Things 3 Cloud System

Cultured Code today announced that it has overhauled the cloud backend of the popular task management app Things 3 using Apple's Swift programming language, with the new system now live across all users' devices.

swift things 3 cultured code
Cultured Code explained that the transition to the new Swift-based infrastructure occurred seamlessly and without any disruption to users. Although the app's behavior remains unchanged on the surface, the underlying service that synchronizes to-do lists across the iPhone, iPad, Mac, Apple Watch, and Apple Vision Pro has been rewritten entirely using Swift and deployed in production for over a year.

The legacy system was originally built using Python 2 and Google App Engine, and had served as the foundation for Things Cloud for more than a decade. While the original synchronization algorithms remain intact and are based on a mathematical model capable of resolving offline edits and conflicts, the aging technology stack was increasingly seen as a barrier to future development. According to Cultured Code, challenges included rising infrastructure costs, slow response times, and the risks associated with dynamic typing in Python.

Apple introduced Swift in 2014; it has since been widely adopted for iOS and macOS app development, but has seen limited uptake in server environments. Cultured Code began experimenting with Swift on the server in 2021, initially rewriting isolated components before committing to a full-scale rebuild.

To ensure a seamless migration, the new Swift system was initially run in parallel with the legacy system, receiving and processing the same data but without taking over user-facing operations. This dual-processing arrangement allowed engineers to validate the new implementation under production-like conditions. Once the team was satisfied with the accuracy and performance of the Swift backend, they transitioned all users to the new system in early 2024.

Cultured Code reports that the new system has achieved significant performance improvements. Traffic peaks of up to 500 requests per second are now handled by a Kubernetes cluster consisting of four nodes, each with two virtual CPUs and 8GB of RAM. This setup has led to a more than threefold reduction in compute costs compared to the legacy system. Synchronization response times have also improved substantially, and the new architecture delivers a fourfold increase in sync request processing speed.

Things has won two Apple design awards. The app is highly regarded for its design consistency and reliable syncing experience across the Apple ecosystem. Read more about the change in Cultured Code's full blog post or its post on Apple's Swift.org blog.

Popular Stories

apple oct 2024 mac tease

Apple Expected to Announce These Two to Three Products 'This Week'

Sunday October 12, 2025 7:05 am PDT by
Apple plans to announce new products "this week," according to Bloomberg's Mark Gurman. Apple's "Mac Your Calendars" teaser last October In his Power On newsletter today, Gurman said the products set to be updated this week include the iPad Pro, Vision Pro, and "likely" the base 14-inch MacBook Pro, with all three likely to receive a spec bump with Apple's next-generation M5 chip. Gurman...
Apple TV Plus Feature 2 Magenta and Blue

Apple TV+ Being Rebranded as Apple TV

Monday October 13, 2025 8:25 am PDT by
Buried in its announcement about "F1: The Movie" making its streaming debut on December 12, Apple has also announced that Apple TV+ is being rebranded as simply Apple TV. A single line near the end of the press release states "Apple TV+ is now simply Apple TV, with a vibrant new identity," though Apple's website has yet to be updated with any changes, so we're unsure on the details of the...
M5 MacBook Pro

Apple Announces New 14-Inch MacBook Pro With M5 Chip

Wednesday October 15, 2025 6:07 am PDT by
Apple today updated the 14-inch MacBook Pro base model with its new M5 chip, which is also available in updated iPad Pro and Vision Pro models. In addition, the base 14-inch MacBook Pro can now be configured with up to 4TB of storage on Apple's online store, whereas the previous model maxed out at 2TB. However, the maximum amount of unified RAM available for this model remains 32GB. Like...
Apple iPad Pro hero M5

Apple Debuts New iPad Pro With M5 Chip, Faster Charging, and More

Wednesday October 15, 2025 6:16 am PDT by
Apple today announced the next-generation iPad Pro, featuring the custom-designed M5, C1X, and N1 chips. The M5 chip has up to a 10-core CPU, with four performance cores and six efficiency cores. It features a next-generation GPU with Neural Accelerator in each core, allowing the new iPad Pro to deliver up to 3.5x the AI performance than the previous model, and a third-generation ray-tracing ...
iOS 26 Feature

Apple Preparing iOS 26.0.2 Update for iPhones

Saturday October 11, 2025 6:59 pm PDT by
Apple's software engineers are internally testing iOS 26.0.2, according to MacRumors logs, which have been a reliable indicator of upcoming iOS versions. iOS 26.0.2 will likely be a minor update that addresses bugs and/or security vulnerabilities, but we do not know any specific details yet. The update will likely be released within the next few weeks. Last month, Apple released iOS...
joz macbook tease

Apple Teases Upcoming M5 MacBook Pro Launch: 'Something Powerful is Coming'

Tuesday October 14, 2025 11:59 am PDT by
Apple marketing chief Greg Joswiak today teased the launch of an upcoming product, saying "something powerful is coming" on social media. Subscribe to the MacRumors YouTube channel for more videos. A short animation accompanying Joswiak's teaser reveals a brief glimpse of a MacBook Pro along with the words "coming soon." The shape of the MacBook Pro is a V, which is the Roman numeral...
airpods max 2024 colors

AirPods Max 2: Everything We Know So Far

Tuesday October 14, 2025 8:43 am PDT by
Apple's AirPods Max have now been available for almost five years, so what do we know about the second-generation version? According to Apple supply chain analyst Ming-Chi Kuo, the new AirPods Max will be lighter than the current ones, but exactly how much is as yet known. The current AirPods Max weigh 0.85 pounds (386.2 grams), excluding the charging case, making it one of the heavier...
iPhone 17 Pro Colors

iPhone 18 Pro Already Rumored to Have These 6 New Features

Saturday October 11, 2025 10:10 am PDT by
While the iPhone 18 Pro and iPhone 18 Pro Max are still nearly a year away, a handful of new features and changes have already been rumored for the devices. Below, we have recapped some of the early iPhone 18 Pro rumors so far. Smaller Dynamic Island The standard iPhone 18, iPhone 18 Pro, and iPhone 18 Pro Max will be equipped with a slightly smaller Dynamic Island, but the devices will...
macbook pro blue

Apple's M5 MacBook Pro Imminent: What to Expect

Tuesday October 14, 2025 4:35 pm PDT by
Apple is going to launch a new version of the MacBook Pro as soon as tomorrow, so we thought we'd go over what to expect from Apple's upcoming Mac. M5 Chip The MacBook Pro will be one of the first new devices to use the next-generation M5 chip, which will replace the M4 chip. The M5 is built on TSMC's more advanced 3-nanometer process, and it will bring speed and efficiency improvements. ...
All AirPods 2025

Apple Reportedly Working on New AirPods Pro, AirPods 5, and H3 Chip

Sunday October 12, 2025 9:24 am PDT by
After releasing AirPods Pro 3 last month, Apple is already working on the next AirPods Pro, according to Bloomberg's Mark Gurman. It is unclear if the new AirPods Pro would be branded as AirPods Pro 4, or if they would be considered an updated version of AirPods Pro 3. Gurman did not take a position, opting to describe them as a "new version" of the "high-end in-ear buds." AirPods Pro 2...

Top Rated Comments

johannnn Avatar
21 weeks ago
Cool.

Maybe now we can get new features? Instead of just "bug fixes" each quarter.
Score: 11 Votes (Like | Disagree)
orbital~debris Avatar
21 weeks ago

No shade but.. it’s a todo list app
No shade but… you haven't seen the sheer quantity of data I've put into said app.
Score: 9 Votes (Like | Disagree)
ignatius345 Avatar
21 weeks ago

Cool.

Maybe now we can get new features? Instead of just "bug fixes" each quarter.
Things is a lean, focused app. They don't just heap random features on constantly. Also, if you haven't noticed it's still a proper software purchase instead of yet another "pay forever" subscription lock-in.

If that means each version is more or less feature-complete when they ship it, I'll happily take that instead of a conveyor belt of new features that gets shovelled out (ready or not) to justify the fact that you're paying "$60/year or whatever.

I'll happily buy Things 4 for iOS and macOS when it comes out, and I also wish it was today. But, at the same time I do trust the developers to release it when it's ready and not before. A lot more Mac software should have this level of attention to detail. If the pace of development we see from Cultured Code keeps quality up and is sustainable for them to stay afloat, so be it.
Score: 7 Votes (Like | Disagree)
gijsmans Avatar
21 weeks ago
It sounds like breakthrough coding but we are taking synchronization of a todo list right?
Score: 6 Votes (Like | Disagree)
tonywalker23 Avatar
21 weeks ago
I am not sure if I am being hyperbolic, or the truthfulness is coming to the surface even when I joke… but I don’t think any app has genuinely impacted my life (with the exception of Logos Bible Software which is my “profession” and got me through graduate school) as much as Things. The fact that its attention to design reminds me of what it was like using a Mac for the first few years in the Aqua days helps.

I probably picked the wrong ‘career’ for someone with thin skin who can’t handle stress well. But, I remember one day a few years ago where I was about to a breaking point when lots of work stuff added up. I called a guy and asked for help and advice. The outcome of that was reading David Allen’s GTD and buying all three versions of Things 3: Mac, iPad, and iPhone.

And here I am today making sure I comment on a Things article. I tried to make Reminders work (and have tried a time or two since then) but keep going back to Things. If your life is chaotic and your never-ending work consist of (gtd vocab) projects with more than one action that need to be done in certain context where start dates and due dates and hard deadlines with consequences all matter, but there is also so much ‘stuff’ hitting your physical and digital inboxes that you need a system to hide items until you need to be reminded of them otherwise your system will be too large to clarify… etc etc blah blah

spend the $80 and buy things for your devices and don’t look back.
Score: 6 Votes (Like | Disagree)
ignatius345 Avatar
21 weeks ago
Huge fan of Things. I used Omnifocus for a long time but found it was just too complex I was spending more time maintaining my system than actually doing stuff. Things is very responsive, low friction, and the UI feels completely native to the Mac. A "Mac-assed app ('https://daringfireball.net/linked/2020/03/20/mac-assed-mac-apps')" if you will.
Score: 6 Votes (Like | Disagree)