[PERF] Eliminate redundant Todos computations by using Onyx derived values

[mountiny]

Background

Todos are computed by analyzing all expense reports in a user's account, iterating through potentially thousands of reports and transactions to determine eligibility. This data is consumed by multiple components with different requirements:

• SearchContext needs the full todos data structure, including all reports, transactions, policies, and related data formatted as search results
• Other components only require simple report counts

Problem

When multiple components need todos-related state on large accounts, if each consumer triggers heavyweight todos computation independently, then render time increases and user-perceived performance degrades.

Solution

Move reusable categorization logic (categorizing reports into submit/approve/pay/export buckets) from the useTodos hook into an Onyx derived value at ONYXKEYS.DERIVED.TODOS. This derived value would compute only the categorized report arrays and transaction mappings at the Onyx level. Components can then use selectors to extract just the report counts from the derived value, avoiding the heavy search results data construction entirely. The useTodos hook would subscribe to this derived value and build the full search results data structure only when required by SearchContext, ensuring the expensive computation runs fewer times.

Results

Tested on iOS exfy-perf heavy account when opening multiple reports in Reports Tab:

Metric	Before	After	Improvement
ManualNavigateToInboxTab span	1.66s	1.23s	26% reduction
useSearchTypeMenuSections total time	700ms	65ms	~91% reduction
openReport span	1.72s	1.49s	8-13% reduction (~200ms depending on report context)
useTodos total time	350ms	9ms	~97% reduction
buildSearchResults total time	53ms	8ms	~85% reduction

Proposal

Slack discussion: https://expensify.slack.com/archives/C05LX9D6E07/p1770106608149389

Issue Owner

Current Issue Owner: @LukasMod

[melvin-bot]

Triggered auto assignment to @stephanieelliott (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.