When writing code and tests, optimize for clarity and idiomatic TypeScript: 1) Prefer `async/await` when the async function includes a side effect. ```ts // Clear: side effect is explicit queryFn: async () => { await sleep(10) fetched = true return 'fetched' } // Less explicit when side effects are involved queryFn: () => sleep(10).then(() => { fetched = true return 'fetched' }) ``` 2) Let TypeScript infer callback types; avoid explicit parameter annotations/imports when they’re redundant. ```ts // Prefer inference onMutate: async (newTodo, context) => { // ... } // If the types infer correctly, remove extra imports/annotations. ``` 3) Simplify type-level assertions by removing unnecessary generics/wrappers; use direct indexed access or the minimal expression that captures the intended type. ```ts // Prefer minimal type plumbing expectTypeOf(queryKey[dataTagSymbol]).toEqualTypeOf>() ```