Why We Chose On-Device Storage Over Cloud-First

Most productivity apps store everything in the cloud. Your tasks, your notes, your habits, all sitting on someone else's server. When we built Halves, we went the other direction. Tasks live on your device first. Here is why, and what that means for you.

The Cloud-First Default

The standard architecture for modern apps is straightforward: user creates data, data goes to a server, server stores it, device fetches it when needed. It works. It scales. It is what most developers reach for because the tooling is mature and the mental model is simple.

But "it works" is not the same as "it is the best choice." Cloud-first storage introduces latency, requires an internet connection, creates a single point of failure, and means a company has access to everything you store. For a task manager that two people use every day, those trade-offs matter more than you might think.

Why On-Device Is Faster

When your tasks are stored locally using Core Data, reading and writing happens at disk speed. There is no network round-trip. No waiting for a server response. No spinner while your task list loads. You open Halves and your tasks are already there, because they never left your phone.

This matters most for the interactions you do dozens of times a day: checking off a task, adding a quick item, scanning your list. Each of those actions should feel instant. With on-device storage, they are. With cloud-first storage, each one depends on network conditions, server load, and API response times. On a slow connection or in airplane mode, a cloud-first app can feel broken. An on-device app just works.

Offline by Default

If your task manager requires an internet connection to show your tasks, it is not a reliable tool. It is a web app with a native wrapper. On-device storage means Halves works in the subway, on a flight, in a basement with no signal. Your data is always accessible because it is always local.

This is not an edge case. People check their task lists in all kinds of connectivity situations. An app that works "most of the time" is an app that eventually lets you down at the worst moment.

Privacy That Is Not Just a Promise

When a company says "we take your privacy seriously," they usually mean "we have a privacy policy." Your data still sits on their servers, accessible to their employees, subject to their security practices, and vulnerable to breaches.

On-device storage changes the equation. If your tasks are stored on your phone, they are protected by your phone's security: your passcode, Face ID, and the device encryption that Apple builds into iOS. Halves does not have access to your tasks because your tasks are not on our servers. Private tasks, which you can mark in the app, are especially protected. They never leave your device. They are not synced, not backed up to our infrastructure, and not visible to your partner. They are truly private.

The Hybrid Approach

A shared task manager for couples obviously needs some form of sync. If your partner adds a task, you need to see it. Pure on-device storage would make that impossible. So Halves uses a hybrid architecture.

The primary data store is Core Data on each device. This is the source of truth for your tasks. For real-time sync between partners, Halves uses Supabase Realtime. When your partner creates, updates, or completes a shared task, the change is pushed to your device through a lightweight real-time channel. Your device receives the update and writes it to its local store. The sync layer is a transport mechanism, not a storage system.

For backup, Halves supports iCloud. Your task data can be backed up to your personal iCloud account, which is encrypted and controlled by you, not by us. If you lose your phone or get a new one, your tasks restore from your iCloud backup just like your photos and messages.

The Trade-Offs

We are not pretending this approach has no downsides. On-device storage means you cannot access your tasks from a web browser. There is no halves.app/dashboard where you log in and see your list. Your tasks live on your phone, and that is where you interact with them.

It also means that if you lose your device and do not have iCloud backup enabled, your data is gone. Cloud-first apps do not have this problem because the server is the backup. With Halves, you need to opt into iCloud backup, and we strongly recommend it.

For our use case, these trade-offs are worth it. A shared task manager for couples is a phone-first experience. You are not managing household tasks from a desktop browser. You are checking things off while standing in the grocery store or lying in bed before sleep. The phone is the right device, and on-device storage makes the phone experience as fast and reliable as possible.

A Philosophy, Not Just a Technical Decision

Choosing on-device storage was a values decision as much as a technical one. We believe your task data is yours. We believe an app should work without an internet connection. We believe speed and privacy are not features to market but baselines to deliver. On-device storage with optional cloud sync is how we deliver on all three. The widgets that show your tasks on your home screen read directly from the local store, which is why they load instantly every time you glance at your phone.