Small changes, big performance wins

Count the calculations

async function resolveRows(estimate, rows) {
  const totals = await calculateEstimate(estimate.id);
  return rows.map((row) => ({
    ...row,
    precomputedTotal: totals.get(row.id),
  }));
}

function resolveTotal(row) {
  if (row.precomputedTotal != null) {
    return row.precomputedTotal; // Zero is valid too.
  }
  return calculateRowTotal(row); // Existing fallback.
}

The parent computes a result for each row and passes it down. The row resolver then reads that value instead of walking the estimate again. A DataLoader can save a database round trip while leaving all of that CPU work intact, so we had to fix both layers.

Here, totals is a map keyed by row ID. That matters too: replacing a repeated calculation with a repeated search through the entire result array can leave another quadratic loop behind. Build the lookup once, then read from it.

The null check is deliberate. A zero total must take the fast path, not fall through because it is falsy. We kept the fallback because rows also arrive through other queries and mutations. The precomputed values travel with this response; they are not a long-lived cache of totals that could go stale after an edit.

One missing ID

 fragment EstimateFragment on Estimate {
+  id
   name
 }

 data: {
+  id: messageId,
   message,
   role,
 },

Apollo normally identifies an entity using its __typename and ID. A name alone is just a value inside a particular response; it does not give the cache a reliable identity to share across queries. Nested entities need their own identity too. Selecting the estimate ID does not identify its contact or organization.

Manual writes need the same care. We added the message ID to the data being written, so it matched what the fragment expected. When investigating this, check the query selection, the actual response, and any code that writes the same entity locally.

Then make the mistake harder to repeat. We enabled the GraphQL operations lint rules with access to our schema and a processor for queries embedded in TypeScript. Custom cache identity fields need matching lint rules. And an ID does not make an incomplete query complete: missing fields and fetch policies still need their own fixes.

Reset the stack, keep the context

// Once the target root is visible, read its active tab.
const root = state.routes[state.index];
const tabState = root.state;
const activeTab = tabState?.routes[tabState.index];

navigation.dispatch(CommonActions.reset({
  index: 0,
  routes: [{
    name: "(tabs)",
    state: {
      index: 0,
      routes: [{
        name: selectedTab,
        params: activeTab?.params,
      }],
    },
  }],
}));

-navigation.navigate(route.name);
+navigation.navigate(route.name, route.params);

The first reset removed the retained screens, but rebuilding a route from its name alone also discarded its parameters. A follow-up carried the active tab’s params into the replacement route. That kept the selected date, view, and filters while still releasing the old detail trees. For a root outside the tab navigator, we preserved the root route’s own params instead.

There were two places to fix. Cleanup had to preserve the destination state, and the navigation controls had to pass it back when revisiting a tab. Otherwise a sidebar or tab press could erase the params before cleanup even ran. On web, we reused only strings and arrays of strings from retained params, rather than copying nested navigation objects into the URL.

The reset still runs only when the intended root is actually visible. We also avoid repeated resets and cancel scheduled cleanup if focus changes. Detail-to-detail navigation keeps its normal stack. The goal is to release the expensive screen trees while keeping the small amount of state that makes returning to a page feel right.

Render less, less often

+<Freeze freeze={!panelOpen}>
   <RowPanelProvider>
     <BottomSheet onDismiss={handleDismiss}>
       <RowForm />
     </BottomSheet>
   </RowPanelProvider>
+</Freeze>

function openPanel() {
  setPanelOpen(true);
  requestAnimationFrame(() => sheetRef.current?.present());
}

function handleDismiss() {
  setPanelOpen(false);
}

The boundary has to include the work you want to stop. Freezing the form alone still leaves its provider free to rerender, derive values, and notify consumers. We moved the boundary above both. The state that controls freezing stayed outside it, so opening the panel could wake the tree back up.

The ordering matters. We set the panel active before presenting it, then froze it from the dismissal callback. Freezing as soon as someone taps Close can catch the sheet halfway through its transition. The animation frame here is the scheduling used by our sheet integration; match this to the lifecycle of the component you use.

This preserves mounted React state, but it does not unsubscribe queries or stop timers. Check which work actually disappeared in the profiler. If the cost comes from a subscription that keeps running while hidden, a render boundary alone will not solve it.

The small PostHog queue

-maxQueueSize: 200,
+maxQueueSize: 30,

const persist = createLatestWriter(writeToDisk);

persist(["event-a"]);                     // Starts writing
persist(["event-a", "event-b"]);          // Waits
persist(["event-a", "event-b", "event-c"]); // Replaces waiting snapshot

// While the first write is still running:
// Disk writes: [a], then [a, b, c]

While one write is running, keep only the newest snapshot waiting behind it. The intermediate copy can go because the latest snapshot already contains its events. Here, the calls overlap before the first write finishes; the helper writes that first snapshot, then the latest one.

This works because each value replaces the whole stored queue. For independent events that each need to be written, dropping the middle one would lose data. Our adapter applied this per storage key, so unrelated files could still write independently.

This bounds the write backlog. It does not remove the cost of creating each snapshot—that is why reducing duplicate events and shrinking the queue mattered too. The example uses arrays to make the behavior visible; PostHog passed our adapter strings it had already serialized.

The hidden weight of an import

-import { UNDERLINE } from "@/design-system/RichTextEditor/transformers";
+import type { TextFormatTransformer } from "@lexical/markdown";
+
+const UNDERLINE: TextFormatTransformer = {
+  format: ["underline"],
+  tag: "_",
+  type: "text-format",
+};

The useful thing to inspect is the path from the DOM entry to the unwanted dependency. Our underline transformer came from a shared module that also reached GraphQL and telemetry. The editor did not need those features, but its import graph still reached them. Keeping this tiny value local cut that path. The import type disappears from the JavaScript output.

We also checked where use dom was declared. It belongs at an intentional DOM boundary, not automatically on every module used by that component. We removed unnecessary directives from helpers and wrappers while keeping the real DOM entry intact.

Rebuild and inspect the output after each change. A smaller-looking source file says little about what ships. Our reported reduction includes both the isolated import and the removed boundaries; it is not a benchmark of this helper alone. For a larger shared helper, a small dependency-free module would be easier to maintain than copying it.

Less type work, faster checks

+type AppPrismaClientOptions = Prisma.PrismaClientOptions & {
+  log: Array<Prisma.LogLevel | Prisma.LogDefinition>;
+  omit?: never;
+};
+
-const client = new PrismaClient(options);
+const client = new PrismaClient<
+  AppPrismaClientOptions, "query", undefined
+>(options);

The expensive part was not the number of lines in the constructor. Prisma’s inferred type described global field-omission configurations we never used. When the client crossed transaction and extension boundaries, TypeScript had to expand and compare those model types.

The third constructor type argument, undefined, makes “no global omissions” explicit. omit?: never stops the options from contradicting that contract. Neither changes the runtime data. We applied the same contract to all five constructors and extension inputs, then narrowed a helper to the one model it used. The measured gain came from the combined change.

Check your generated Prisma definitions before copying the generic positions: the constructor and exported type alias use different ones. We added a compile-time check to catch the omission type widening again and compared emitted JavaScript. When measuring, keep the compiler and cold-cache settings fixed and inspect --extendedDiagnostics; otherwise a warm run can look like a type optimization.