diff --git a/perf-testing/rtkq-testing.mjs b/perf-testing/rtkq-testing.mjs
new file mode 100644
index 00000000..040a8940
--- /dev/null
+++ b/perf-testing/rtkq-testing.mjs
@@ -0,0 +1,127 @@
+import {produce} from "../dist/immer.mjs"
+
+function createInitialState(arraySize = BENCHMARK_CONFIG.arraySize) {
+	const initialState = {
+		largeArray: Array.from({length: arraySize}, (_, i) => ({
+			id: i,
+			value: Math.random(),
+			nested: {key: `key-${i}`, data: Math.random()},
+			moreNested: {
+				items: Array.from(
+					{length: BENCHMARK_CONFIG.nestedArraySize},
+					(_, i) => ({id: i, name: String(i)})
+				)
+			}
+		})),
+		otherData: Array.from({length: arraySize}, (_, i) => ({
+			id: i,
+			name: `name-${i}`,
+			isActive: i % 2 === 0
+		})),
+		api: {
+			queries: {},
+			provided: {
+				keys: {}
+			},
+			subscriptions: {}
+		}
+	}
+	return initialState
+}
+
+const MAX = 1
+
+const BENCHMARK_CONFIG = {
+	iterations: 1,
+	arraySize: 100,
+	nestedArraySize: 10,
+	multiUpdateCount: 5,
+	reuseStateIterations: 10
+}
+
+// RTKQ-style action creators
+const rtkqPending = index => ({
+	type: "rtkq/pending",
+	payload: {
+		cacheKey: `some("test-${index}-")`,
+		requestId: `req-${index}`,
+		id: `test-${index}-`
+	}
+})
+
+const rtkqResolved = index => ({
+	type: "rtkq/resolved",
+	payload: {
+		cacheKey: `some("test-${index}-")`,
+		requestId: `req-${index}`,
+		id: `test-${index}-`,
+		data: `test-${index}-1`
+	}
+})
+
+const createImmerReducer = produce => {
+	const immerReducer = (state = createInitialState(), action) =>
+		produce(state, draft => {
+			switch (action.type) {
+				case "rtkq/pending": {
+					// Simulate separate RTK slice reducers with combined reducer pattern
+					const cacheKey = action.payload.cacheKey
+					draft.api.queries[cacheKey] = {
+						id: action.payload.id,
+						status: "pending",
+						data: undefined
+					}
+					draft.api.provided.keys[cacheKey] = {}
+					draft.api.subscriptions[cacheKey] = {
+						[action.payload.requestId]: {
+							pollingInterval: 0,
+							skipPollingIfUnfocused: false
+						}
+					}
+					break
+				}
+				case "rtkq/resolved": {
+					const cacheKey = action.payload.cacheKey
+					draft.api.queries[cacheKey].status = "fulfilled"
+					draft.api.queries[cacheKey].data = action.payload.data
+					// provided and subscriptions don't change on resolved
+					break
+				}
+			}
+		})
+
+	return immerReducer
+}
+
+const immerReducer = createImmerReducer(produce)
+const initialState = createInitialState()
+
+const arraySizes = [10, 100, 250, 500, 1000, 1021, 1500, 2000, 3000]
+
+for (const arraySize of arraySizes) {
+	console.log(`Running benchmark with array size: ${arraySize}`)
+
+	const start = performance.now()
+
+	let state = initialState
+
+	// Phase 1: Execute all pending actions
+	for (let i = 0; i < arraySize; i++) {
+		state = immerReducer(state, rtkqPending(i))
+	}
+
+	// Phase 2: Execute all resolved actions
+	for (let i = 0; i < arraySize; i++) {
+		state = immerReducer(state, rtkqResolved(i))
+	}
+
+	const end = performance.now()
+	const total = end - start
+	const avg = total / arraySize
+
+	console.log(
+		`Done in ${total.toFixed(1)} ms (items: ${arraySize}, avg: ${avg.toFixed(
+			3
+		)} ms / item)`
+	)
+}
diff --git a/src/core/immerClass.ts b/src/core/immerClass.ts
index 64c221f1..43df8c82 100644
--- a/src/core/immerClass.ts
+++ b/src/core/immerClass.ts
@@ -31,7 +31,12 @@ interface ProducersFns {
 	produceWithPatches: IProduceWithPatches
 }
 
-export type StrictMode = boolean | "class_only"
+export type StrictMode =
+	| boolean
+	| "class_only"
+	| "strings_only"
+	| "with_symbols"
+	| "full"
 
 export class Immer implements ProducersFns {
 	autoFreeze_: boolean = true
@@ -45,7 +50,7 @@ export class Immer implements ProducersFns {
 	}) {
 		if (typeof config?.autoFreeze === "boolean")
 			this.setAutoFreeze(config!.autoFreeze)
-		if (typeof config?.useStrictShallowCopy === "boolean")
+		if (typeof config?.useStrictShallowCopy !== "undefined")
 			this.setUseStrictShallowCopy(config!.useStrictShallowCopy)
 		if (typeof config?.useStrictIteration === "boolean")
 			this.setUseStrictIteration(config!.useStrictIteration)
diff --git a/src/utils/common.ts b/src/utils/common.ts
index 7bb5f93d..658ecfcd 100644
--- a/src/utils/common.ts
+++ b/src/utils/common.ts
@@ -164,7 +164,11 @@ export function shallowCopy(base: any, strict: StrictMode) {
 
 	const isPlain = isPlainObject(base)
 
-	if (strict === true || (strict === "class_only" && !isPlain)) {
+	if (
+		strict === true ||
+		strict === "full" ||
+		(strict === "class_only" && !isPlain)
+	) {
 		// Perform a strict copy
 		const descriptors = Object.getOwnPropertyDescriptors(base)
 		delete descriptors[DRAFT_STATE as any]
@@ -192,6 +196,25 @@ export function shallowCopy(base: any, strict: StrictMode) {
 		// perform a sloppy copy
 		const proto = getPrototypeOf(base)
 		if (proto !== null && isPlain) {
+			// v8 has a perf cliff at 1020 properties where it
+			// switches from "fast properties" to "dictionary mode" at 1020 keys:
+			// - https://github.com/v8/v8/blob/754e7ba956b06231c487e09178aab9baba1f46fe/src/objects/property-details.h#L242-L247
+			// - https://github.com/v8/v8/blob/754e7ba956b06231c487e09178aab9baba1f46fe/test/mjsunit/dictionary-prototypes.js
+			// At that size, object spread gets drastically slower,
+			// and an `Object.keys()` loop becomes _faster_.
+			// Immer currently expects that we also copy symbols.  That would require either a `Reflect.ownKeys()`,
+			// or `.keys()` + `.getOwnPropertySymbols()`.
+			// For v10.x, we can keep object spread the default,
+			// and offer an option to switch to just strings to enable better perf
+			// with larger objects. For v11, we can flip those defaults.
+			if (strict === "strings_only") {
+				const copy: Record<string | symbol, any> = {}
+				Object.keys(base).forEach(key => {
+					copy[key] = base[key]
+				})
+				return copy
+			}
+
 			return {...base} // assumption: better inner class optimization than the assign below
 		}
 		const obj = Object.create(proto)