diff --git a/packages/core/src/execution-engine/node-execution-context/utils/__tests__/validate-value-against-schema.test.ts b/packages/core/src/execution-engine/node-execution-context/utils/__tests__/validate-value-against-schema.test.ts
index 1037bedd92d..aea4e67142b 100644
--- a/packages/core/src/execution-engine/node-execution-context/utils/__tests__/validate-value-against-schema.test.ts
+++ b/packages/core/src/execution-engine/node-execution-context/utils/__tests__/validate-value-against-schema.test.ts
@@ -464,5 +464,136 @@ describe('validateValueAgainstSchema', () => {
 				).toThrow("Invalid input for 'count' [item 0]");
 			});
 		});
+
+		describe('schema field lookup', () => {
+			const nodeType = {
+				description: {
+					properties: [
+						{
+							displayName: 'Columns',
+							name: 'columns',
+							type: 'resourceMapper',
+							typeOptions: {
+								resourceMapper: {
+									mode: 'add',
+								},
+							},
+						},
+					],
+				},
+			} as unknown as INodeType;
+
+			const schemaField = (id: string, type: string, required = false) => ({
+				id,
+				displayName: id,
+				required,
+				defaultMatch: false,
+				display: true,
+				type,
+				canBeUsedToMatch: false,
+			});
+
+			const makeNode = (schema: unknown[], value: IDataObject) =>
+				({
+					parameters: {
+						columns: {
+							mappingMode: 'defineBelow',
+							value,
+							matchingColumns: [],
+							attemptToConvertTypes: false,
+							schema,
+						},
+						options: {},
+					},
+					id: '8d6cec63-8db1-440c-8966-4d6311ee69a9',
+					name: 'add products to DB',
+					type: 'n8n-nodes-base.postgres',
+					typeVersion: 2.3,
+					position: [420, 0],
+				}) as unknown as INode;
+
+			const parameterName = 'columns.value';
+
+			test('resolves every value against its own schema entry, whatever its position', () => {
+				const schema = [
+					schemaField('a', 'number'),
+					schemaField('b', 'string'),
+					schemaField('c', 'number'),
+					schemaField('d', 'boolean'),
+				];
+				const value = { d: 'true', c: '3', b: 2, a: '1' };
+
+				const result = validateValueAgainstSchema(
+					makeNode(schema, value),
+					nodeType,
+					value,
+					parameterName,
+					0,
+					0,
+				);
+
+				// `a`, `c` and `d` are cast to their schema type; `b` keeps its type, as
+				// validateFieldType does not coerce values for string fields.
+				expect(result).toEqual({ a: 1, b: 2, c: 3, d: true });
+			});
+
+			test('uses the first entry when a field id appears twice, like Array.prototype.find', () => {
+				const schema = [schemaField('dup', 'number'), schemaField('dup', 'string')];
+				const value = { dup: '42' };
+
+				const result = validateValueAgainstSchema(
+					makeNode(schema, value),
+					nodeType,
+					value,
+					parameterName,
+					0,
+					0,
+				);
+
+				// The first entry types `dup` as a number, so the string is cast. Had the second
+				// (string) entry won, the value would have stayed '42'.
+				expect(result).toEqual({ dup: 42 });
+			});
+
+			test('leaves values that have no schema entry untouched', () => {
+				const schema = [schemaField('known', 'number')];
+				const value = { known: '7', unknown: 'abc' };
+
+				const result = validateValueAgainstSchema(
+					makeNode(schema, value),
+					nodeType,
+					value,
+					parameterName,
+					0,
+					0,
+				);
+
+				expect(result).toEqual({ known: 7, unknown: 'abc' });
+			});
+
+			// `isResourceMapperValue` only checks that `schema` is present, so a persisted
+			// `schema: null` reaches the lookup. Indexing now runs before the loop, where the
+			// previous `schema.find` only ran inside it — an empty value never touched it.
+			describe.each([
+				['null', null],
+				['undefined', undefined],
+				['empty', []],
+			])('when the stored schema is %s', (_label, schema) => {
+				test('resolves no field instead of throwing', () => {
+					const value = { anything: 'kept' };
+
+					const result = validateValueAgainstSchema(
+						makeNode(schema as unknown as unknown[], value),
+						nodeType,
+						value,
+						parameterName,
+						0,
+						0,
+					);
+
+					expect(result).toEqual({ anything: 'kept' });
+				});
+			});
+		});
 	});
 });
diff --git a/packages/core/src/execution-engine/node-execution-context/utils/validate-value-against-schema.ts b/packages/core/src/execution-engine/node-execution-context/utils/validate-value-against-schema.ts
index 5f0e2a9bba1..30a35e902d0 100644
--- a/packages/core/src/execution-engine/node-execution-context/utils/validate-value-against-schema.ts
+++ b/packages/core/src/execution-engine/node-execution-context/utils/validate-value-against-schema.ts
@@ -6,6 +6,7 @@ import type {
 	INodePropertyCollection,
 	INodePropertyOptions,
 	INodeType,
+	ResourceMapperField,
 	ResourceMapperTypeOptions,
 } from 'n8n-workflow';
 import {
@@ -17,6 +18,31 @@ import {
 
 import type { ExtendedValidationResult } from '@/interfaces';
 
+const schemaIndexCache = new WeakMap<ResourceMapperField[], Map<string, ResourceMapperField>>();
+
+const EMPTY_SCHEMA_INDEX: ReadonlyMap<string, ResourceMapperField> = new Map();
+
+const indexSchemaById = (
+	schema: ResourceMapperField[] | undefined,
+): ReadonlyMap<string, ResourceMapperField> => {
+	// `isResourceMapperValue` only checks that `schema` is present, so a persisted
+	// `schema: null` reaches this. Indexing runs before the loop now, where the previous
+	// `schema.find` only ran inside it, so bail out here instead of throwing on iteration.
+	if (!schema?.length) {
+		return EMPTY_SCHEMA_INDEX;
+	}
+	let index = schemaIndexCache.get(schema);
+	if (!index) {
+		index = new Map<string, ResourceMapperField>();
+		for (const entry of schema) {
+			// First occurrence wins, matching the `schema.find` this index replaces
+			if (!index.has(entry.id)) index.set(entry.id, entry);
+		}
+		schemaIndexCache.set(schema, index);
+	}
+	return index;
+};
+
 const validateResourceMapperValue = (
 	parameterName: string,
 	paramValues: { [key: string]: unknown },
@@ -35,13 +61,13 @@ const validateResourceMapperValue = (
 	if (!resourceMapperField || !isResourceMapperValue(resourceMapperField)) {
 		return result;
 	}
-	const schema = resourceMapperField.schema;
+	const schemaById = indexSchemaById(resourceMapperField.schema);
 	const paramValueNames = Object.keys(paramValues);
 	for (let i = 0; i < paramValueNames.length; i++) {
 		const key = paramValueNames[i];
 		const resolvedValue = paramValues[key];
 
-		const schemaEntry = schema.find((s) => s.id === key);
+		const schemaEntry = schemaById.get(key);
 
 		if (
 			!skipRequiredCheck &&