[Due for payment 2025-07-14] [$250] Improve the subscribeToKey efficiency in Onyx

[mountiny]

Coming from this proposal

Problem

Onyx.connect uses subscribeToKey to subscribe to keys, but it performs an O(n) iteration over all Onyx keys - even for exact key matches.
This inefficiency becomes a major bottleneck on screens with many Onyx connections (e.g., screens with lists having per-item subscriptions). When entering expense chat on an account with 40k Onyx keys, it spends 900ms looping through them multiple times.

Solution

Optimize subscribeToKey by distinguishing between:

• Non-collection keys - use direct lookup instead of iterating through all keys
• Collection keys - use current iteration logic

Tested on iOS simulator with 40k keys:

• App launch: isKeyMatch total time dropped from 770ms to 330ms
• Expense report screen: isKeyMatch dropped from 900ms to 35ms

Upwork Automation - Do Not Edit

• Upwork Job URL: https://www.upwork.com/jobs/~021937284236503470296
• Upwork Job ID: 1937284236503470296
• Last Price Increase: 2025-06-23

Issue Owner

Current Issue Owner: @adelekennedy

[melvin-bot]

Job added to Upwork: https://www.upwork.com/jobs/~021937284236503470296

[melvin-bot]

Triggered auto assignment to Contributor-plus team member for initial proposal review - @ikevin127 (External)

[melvin-bot]

Triggered auto assignment to @adelekennedy (Bug), see https://stackoverflow.com/c/expensify/questions/14418 for more details. Please add this bug to a GH project, as outlined in the SO.