Problem

Two compounding problems drove the rebuild. First, the existing implementation had two sources of truth — a React context and a Redux store — that were meant to stay in sync but would drift, causing the app to loop as it tried to reconcile them. It was brittle and hard to reason about. Second, business users had a real unmet need: the original reports were just a chart with a flat transaction list underneath. For accounting purposes and deep financial analysis, users needed something much closer to Excel pivot table behavior — the ability to change rows, columns, and groupings interactively while the chart updated alongside.

Approach

Eliminated the dual source-of-truth problem by consolidating all report state into Redux, removing the React context layer entirely. Then built an interactive data grid on top of that stable foundation — supporting drill-down into categories, dynamic row and column configuration, and filtering — all while keeping the chart in sync with whatever view the grid was showing. The chart and grid share the same derived state, so they always agree.

Outcome

Delivered a reports experience that genuinely works for power users doing accounting and financial analysis — not just a chart with a table below it, but an interactive pivot-style view. Resolved the state synchronization bugs that had been a persistent source of issues, and established a cleaner architecture for the feature going forward.

Problem

Spending Plan, Simplifi's primary monthly budgeting view, had a persistent 2-second lag on common interactions. The page was designed to be highly interactive — users are constantly adjusting values and seeing the effect on their budget — but every interaction was round-tripping to the server for recalculation, making it feel sluggish and unresponsive.

Approach

The key insight was that we didn't need the server for this. Transactions were already loaded client-side as part of our existing client-first architecture, and we had already built optimistic update patterns on the transactions page that we could leverage directly. The fix was moving budget calculations entirely to the client — computing derived state from the transaction data already in Redux rather than waiting on a server response. Added a comprehensive Jest test suite and coordinated a cross-team test plan to validate correctness of the client-side calculations.

Outcome

Interaction latency dropped from 2 seconds to under 50ms — a 40× improvement. Because the approach reused existing optimistic update infrastructure rather than building something new, it was lower risk than it sounds and shipped cleanly. The test suite became the standard for the feature going forward.