diff --git a/packages/core/src/backend/common.ts b/packages/core/src/backend/common.ts
index 227d069..942e9d6 100644
--- a/packages/core/src/backend/common.ts
+++ b/packages/core/src/backend/common.ts
@@ -1,5 +1,12 @@
 import {BaseSchema} from 'valibot';
-import {ApplicationState, ContentNegotiation, Language, LanguageStatusMessageMap, Resource} from '../common';
+import {
+	ApplicationState,
+	BaseResourceType,
+	ContentNegotiation,
+	Language,
+	LanguageStatusMessageMap,
+	Resource,
+} from '../common';
 import {DataSource} from './data-source';
 
 export interface BackendState {
@@ -45,8 +52,8 @@ export type Method = 'GET' | 'POST' | 'PUT' | 'PATCH' | 'DELETE' | 'OPTIONS' | '
 export interface AllowedMiddlewareSpecification<Schema extends BaseSchema = BaseSchema> {
 	method: Method;
 	middleware: Middleware;
-	constructBodySchema?: (resource: Resource<Schema>, resourceId?: string) => BaseSchema;
-	allowed: (resource: Resource<Schema>) => boolean;
+	constructBodySchema?: (resource: Resource<BaseResourceType & { schema: Schema }>, resourceId?: string) => BaseSchema;
+	allowed: (resource: Resource<BaseResourceType & { schema: Schema }>) => boolean;
 }
 
 export interface Response {
diff --git a/packages/core/src/backend/servers/http/core.ts b/packages/core/src/backend/servers/http/core.ts
index 1509784..b7c506a 100644
--- a/packages/core/src/backend/servers/http/core.ts
+++ b/packages/core/src/backend/servers/http/core.ts
@@ -9,7 +9,14 @@ import {
 	RequestContext, RequestDecorator,
 	Response,
 } from '../../common';
-import {CanPatchSpec, DELTA_SCHEMA, PATCH_CONTENT_MAP_TYPE, PatchContentType, Resource} from '../../../common';
+import {
+	BaseResourceType,
+	CanPatchSpec,
+	DELTA_SCHEMA,
+	PATCH_CONTENT_MAP_TYPE,
+	PatchContentType,
+	Resource,
+} from '../../../common';
 import {
 	handleGetRoot, handleOptions,
 } from './handlers/default';
@@ -49,11 +56,11 @@ declare module '../../common' {
 	}
 }
 
-const constructPostSchema = <T extends v.BaseSchema>(resource: Resource<T>) => {
+const constructPostSchema = <T extends v.BaseSchema>(resource: Resource<BaseResourceType & { schema: T }>) => {
 	return resource.schema;
 };
 
-const constructPutSchema = <T extends v.BaseSchema>(resource: Resource<T>, mainResourceId?: string) => {
+const constructPutSchema = <T extends v.BaseSchema>(resource: Resource<BaseResourceType & { schema: T }>, mainResourceId?: string) => {
 	if (typeof mainResourceId === 'undefined') {
 		return resource.schema;
 	}
@@ -77,7 +84,7 @@ const constructPutSchema = <T extends v.BaseSchema>(resource: Resource<T>, mainR
 	);
 };
 
-const constructPatchSchema = <T extends v.BaseSchema>(resource: Resource<T>) => {
+const constructPatchSchema = <T extends v.BaseSchema>(resource: Resource<BaseResourceType & { schema: T }>) => {
 	const schema = resource.schema.type === 'object' ? resource.schema as unknown as v.ObjectSchema<any> : resource.schema;
 
 	if (resource.schema.type !== 'object') {
diff --git a/packages/core/src/common/app.ts b/packages/core/src/common/app.ts
index beecd69..94beaf1 100644
--- a/packages/core/src/common/app.ts
+++ b/packages/core/src/common/app.ts
@@ -1,4 +1,4 @@
-import {Resource} from './resource';
+import {BaseResourceType, Resource} from './resource';
 import {FALLBACK_LANGUAGE, Language} from './language';
 import {FALLBACK_MEDIA_TYPE, MediaType, PATCH_CONTENT_TYPES} from './media-type';
 import {Charset, FALLBACK_CHARSET} from './charset';
@@ -35,12 +35,8 @@ export interface Application<
 	charset<CharsetName extends string = string>(charset: Charset<CharsetName>): Application<
 		Resources, MediaTypes, [...Charsets, Charset<CharsetName>], Languages
 	>;
-	resource<
-		Schema extends v.BaseSchema,
-		CurrentItemName extends string = string,
-		CurrentRouteName extends string = string
-	>(resRaw: Resource<Schema, CurrentItemName, CurrentRouteName>): Application<
-		[...Resources, Resource<Schema, CurrentItemName, CurrentRouteName>], MediaTypes, Charsets, Languages
+	resource<ResourceType extends BaseResourceType = BaseResourceType>(resRaw: Resource<ResourceType>): Application<
+		[...Resources, Resource<ResourceType>], MediaTypes, Charsets, Languages
 	>;
 	createBackend(params: Omit<CreateBackendParams, 'app'>): Backend;
 	createClient(params: Omit<CreateClientParams, 'app'>): ClientBuilder;
@@ -84,7 +80,7 @@ export const application = (appParams: ApplicationParams): Application => {
 			appState.languages.set(language.name, language);
 			return this;
 		},
-		resource<T extends v.BaseSchema>(resRaw: Resource<T>) {
+		resource<T extends v.BaseSchema>(resRaw: Resource<BaseResourceType & { schema: T }>) {
 			appState.resources.add(resRaw);
 			return this;
 		},
diff --git a/packages/core/src/common/resource.ts b/packages/core/src/common/resource.ts
index ddceabe..e5b4fe5 100644
--- a/packages/core/src/common/resource.ts
+++ b/packages/core/src/common/resource.ts
@@ -31,36 +31,38 @@ export interface ResourceState<
 
 type CanPatch = boolean | Partial<CanPatchObject> | CanPatchSpec[];
 
-export interface Resource<
-	Schema extends v.BaseSchema = v.BaseSchema,
-	CurrentName extends string = string,
-	CurrentRouteName extends string = string,
-	CurrentIdAttr extends string = string,
-	IdSchema extends v.BaseSchema = v.BaseSchema
-> {
-	schema: Schema;
-	state: ResourceState<CurrentName, CurrentRouteName>;
-	name<NewName extends CurrentName>(n: NewName): Resource<Schema, NewName, CurrentRouteName, CurrentIdAttr, IdSchema>;
-	route<NewRouteName extends CurrentRouteName>(n: NewRouteName): Resource<Schema, CurrentName, NewRouteName, CurrentIdAttr, IdSchema>;
+export interface BaseResourceType {
+	schema: v.BaseSchema;
+	name: string;
+	routeName: string;
+	idAttr: string;
+	idSchema: v.BaseSchema;
+	createdAtAttr: string;
+	updatedAtAttr: string;
+}
+
+export interface Resource<ResourceType extends BaseResourceType = BaseResourceType> {
+	schema: ResourceType['schema'];
+	state: ResourceState<ResourceType['name'], ResourceType['routeName']>;
+	name<NewName extends ResourceType['name']>(n: NewName): Resource<ResourceType & { name: NewName }>;
+	route<NewRouteName extends ResourceType['routeName']>(n: NewRouteName): Resource<ResourceType & { routeName: NewRouteName }>;
 	canFetchCollection(b?: boolean): this;
 	canFetchItem(b?: boolean): this;
 	canCreate(b?: boolean): this;
 	canPatch(b?: CanPatch): this;
 	canEmplace(b?: boolean): this;
 	canDelete(b?: boolean): this;
-	relatedTo<RelatedSchema extends v.BaseSchema>(resource: Resource<RelatedSchema>): this;
+	relatedTo<RelatedSchema extends v.BaseSchema>(resource: Resource<ResourceType & { schema: RelatedSchema }>): this;
 	dataSource?: DataSource;
-	id<NewIdAttr extends CurrentIdAttr, TheIdSchema extends IdSchema>(
+	id<NewIdAttr extends ResourceType['idAttr'], TheIdSchema extends ResourceType['idSchema']>(
 		newIdAttr: NewIdAttr,
 		params: ResourceIdConfig<TheIdSchema>
-	): Resource<Schema, CurrentName, CurrentRouteName, NewIdAttr, TheIdSchema>;
+	): Resource<ResourceType & { idAttr: NewIdAttr, idSchema: TheIdSchema }>;
+	createdAt<NewCreatedAtAttr extends ResourceType['createdAtAttr']>(n: NewCreatedAtAttr): Resource<ResourceType & { createdAtAttr: NewCreatedAtAttr }>;
+	updatedAt<NewUpdatedAtAttr extends ResourceType['updatedAtAttr']>(n: NewUpdatedAtAttr): Resource<ResourceType & { updatedAtAttr: NewUpdatedAtAttr }>;
 }
 
-export const resource = <
-	Schema extends v.BaseSchema,
-	CurrentName extends string = string,
-	CurrentRouteName extends string = string
->(schema: Schema): Resource<Schema, CurrentName, CurrentRouteName> => {
+export const resource = <ResourceType extends BaseResourceType = BaseResourceType>(schema: ResourceType['schema']): Resource<ResourceType> => {
 	const resourceState = {
 		shared: new Map(),
 		relationships: new Set<Resource>(),
@@ -73,13 +75,11 @@ export const resource = <
 		},
 		canEmplace: false,
 		canDelete: false,
-	} as ResourceState<CurrentName, CurrentRouteName>;
+	} as ResourceState<ResourceType['name'], ResourceType['routeName']>;
 
 	return {
-		get state(): ResourceState<CurrentName, CurrentRouteName> {
-			return Object.freeze({
-				...resourceState
-			}) as unknown as ResourceState<CurrentName, CurrentRouteName>;
+		get state(): ResourceState<ResourceType['name'], ResourceType['routeName']> {
+			return Object.freeze(resourceState);
 		},
 		canFetchCollection(b = true) {
 			resourceState.canFetchCollection = b;
@@ -135,13 +135,13 @@ export const resource = <
 			resourceState.shared.set('fullText', fullTextAttrs);
 			return this;
 		},
-		name<NewName extends CurrentName>(n: NewName) {
+		name<NewName extends ResourceType['name']>(n: NewName) {
 			resourceState.itemName = n;
-			return this as Resource<Schema, NewName, CurrentRouteName>;
+			return this;
 		},
-		route<NewRouteName extends CurrentRouteName>(n: NewRouteName) {
+		route<NewRouteName extends ResourceType['routeName']>(n: NewRouteName) {
 			resourceState.routeName = n;
-			return this as Resource<Schema, CurrentName, NewRouteName>;
+			return this;
 		},
 		get itemName() {
 			return resourceState.itemName;
@@ -152,11 +152,19 @@ export const resource = <
 		get schema() {
 			return schema;
 		},
-		relatedTo<RelatedSchema extends v.BaseSchema>(resource: Resource<RelatedSchema>) {
+		relatedTo<RelatedSchema extends v.BaseSchema>(resource: Resource<ResourceType & { schema: RelatedSchema }>) {
 			resourceState.relationships.add(resource);
 			return this;
 		},
-	} as Resource<Schema, CurrentName, CurrentRouteName>;
+		createdAt<NewCreatedAtAttr extends ResourceType['createdAtAttr']>(n: NewCreatedAtAttr) {
+			resourceState.shared.set('createdAtAttr', n);
+			return this;
+		},
+		updatedAt<NewUpdatedAtAttr extends ResourceType['updatedAtAttr']>(n: NewUpdatedAtAttr) {
+			resourceState.shared.set('updatedAtAttr', n);
+			return this;
+		},
+	} as Resource<ResourceType>;
 };
 
 export type ResourceType<R extends Resource> = v.Output<R['schema']>;
diff --git a/packages/data-sources/file-jsonl/src/index.ts b/packages/data-sources/file-jsonl/src/index.ts
index eefadd4..66973ad 100644
--- a/packages/data-sources/file-jsonl/src/index.ts
+++ b/packages/data-sources/file-jsonl/src/index.ts
@@ -1,6 +1,6 @@
 import { readFile, writeFile } from 'fs/promises';
 import { join } from 'path';
-import { Resource, validation as v } from '@modal-sh/yasumi';
+import { Resource, validation as v, BaseResourceType } from '@modal-sh/yasumi';
 import { DataSource, ResourceIdConfig } from '@modal-sh/yasumi/backend';
 import assert from 'assert';
 
@@ -16,7 +16,11 @@ export class JsonLinesDataSource<
 > implements DataSource<Data> {
   private path?: string;
 
-  private resource?: Resource<Schema, CurrentName, CurrentRouteName>;
+  private resource?: Resource<BaseResourceType & {
+    schema: Schema,
+    name: CurrentName,
+    routeName: CurrentRouteName,
+  }>;
 
   data: Data[] = [];
 
@@ -24,15 +28,25 @@ export class JsonLinesDataSource<
     // noop
   }
 
-  prepareResource(resource: Resource<Schema, CurrentName, CurrentRouteName>) {
+  prepareResource<Schema extends v.BaseSchema>(resource: Resource<BaseResourceType & {
+    schema: Schema,
+    name: CurrentName,
+    routeName: CurrentRouteName,
+  }>) {
     this.path = join(this.baseDir, `${resource.state.routeName}.jsonl`);
     resource.dataSource = resource.dataSource ?? this;
     const originalResourceId = resource.id;
-    resource.id = <NewIdAttr extends string, NewIdSchema extends v.BaseSchema>(newIdAttr: NewIdAttr, params: ResourceIdConfig<NewIdSchema>) => {
+    resource.id = <NewIdAttr extends BaseResourceType['idAttr'], NewIdSchema extends BaseResourceType['idSchema']>(newIdAttr: NewIdAttr, params: ResourceIdConfig<NewIdSchema>) => {
       originalResourceId(newIdAttr, params);
-      return resource as Resource<Schema, CurrentName, CurrentRouteName, NewIdAttr, NewIdSchema>;
+      return resource as Resource<BaseResourceType & {
+        name: CurrentName,
+        routeName: CurrentRouteName,
+        schema: Schema,
+        idAttr: NewIdAttr,
+        idSchema: NewIdSchema,
+      }>;
     };
-    this.resource = resource;
+    this.resource = resource as any;
   }
 
   async initialize() {
@@ -94,12 +108,28 @@ export class JsonLinesDataSource<
     const idConfig = this.resource.state.shared.get('idConfig') as ResourceIdConfig<any> | undefined;
     assert(typeof idConfig !== 'undefined', new ResourceIdNotDesignatedError());
 
+    let theId: any;
+    const { [idAttr]: dataId, ...etcData } = data as Record<string, unknown>;
+    if (typeof dataId !== 'undefined') {
+      theId = idConfig.deserialize((data as Record<string, string>)[idAttr]);
+    } else {
+      const newId = await this.newId();
+      theId = idConfig.deserialize(newId);
+    }
     const newData = {
-      ...data
+      [idAttr]: theId,
+      ...etcData
     } as Record<string, unknown>;
 
-    if (idAttr in newData) {
-      newData[idAttr] = idConfig.deserialize(newData[idAttr] as string);
+    const now = Date.now(); // TODO how to serialize dates
+    const createdAt = this.resource.state.shared.get('createdAtAttr');
+    if (typeof createdAt === 'string') {
+      newData[createdAt] = now;
+    }
+
+    const updatedAt = this.resource.state.shared.get('updatedAtAttr');
+    if (typeof updatedAt === 'string') {
+      newData[updatedAt] = now;
     }
 
     const newCollection = [
@@ -109,7 +139,7 @@ export class JsonLinesDataSource<
 
     await writeFile(this.path, newCollection.map((d) => JSON.stringify(d)).join('\n'));
 
-    return data as Data;
+    return newData as Data;
   }
 
   async delete(idSerialized: string) {
@@ -148,9 +178,20 @@ export class JsonLinesDataSource<
     const dataToEmplace = {
       [idAttr]: id,
       ...data,
-    } as Data;
+    } as Record<string, unknown>;
 
     if (existing) {
+      const createdAt = this.resource.state.shared.get('createdAtAttr');
+      if (typeof createdAt === 'string') {
+        dataToEmplace[createdAt] = (existing as Record<string, unknown>)[createdAt];
+      }
+
+      const now = Date.now(); // TODO how to serialize dates
+      const updatedAt = this.resource.state.shared.get('updatedAtAttr');
+      if (typeof updatedAt === 'string') {
+        dataToEmplace[updatedAt] = now;
+      }
+
       const newData = this.data.map((d) => {
         if ((d as any)[idAttr] === id) {
           return dataToEmplace;
@@ -164,7 +205,7 @@ export class JsonLinesDataSource<
       return [dataToEmplace, false] as [Data, boolean];
     }
 
-    const newData = await this.create(dataToEmplace);
+    const newData = await this.create(dataToEmplace as Data);
     return [newData, true] as [Data, boolean];
   }
 
@@ -186,6 +227,17 @@ export class JsonLinesDataSource<
     const newItem = {
       ...existing,
       ...data,
+    } as Record<string, unknown>;
+
+    const createdAt = this.resource.state.shared.get('createdAtAttr');
+    if (typeof createdAt === 'string') {
+      newItem[createdAt] = (existing as Record<string, unknown>)[createdAt];
+    }
+
+    const now = Date.now(); // TODO how to serialize dates
+    const updatedAt = this.resource.state.shared.get('updatedAtAttr');
+    if (typeof updatedAt === 'string') {
+      newItem[updatedAt] = now;
     }
 
     const id = idConfig.deserialize(idSerialized);
diff --git a/packages/data-sources/file-jsonl/test/index.test.ts b/packages/data-sources/file-jsonl/test/index.test.ts
index 1b3c126..1b861d6 100644
--- a/packages/data-sources/file-jsonl/test/index.test.ts
+++ b/packages/data-sources/file-jsonl/test/index.test.ts
@@ -1,7 +1,7 @@
 import {describe, it, expect, vi, Mock, beforeAll, beforeEach} from 'vitest';
 import { readFile, writeFile } from 'fs/promises';
 import { JsonLinesDataSource } from '../src';
-import { resource, validation as v } from '@modal-sh/yasumi';
+import { resource, validation as v, BaseResourceType } from '@modal-sh/yasumi';
 import {DataSource} from '@modal-sh/yasumi/dist/types/backend';
 
 vi.mock('fs/promises');
@@ -51,7 +51,7 @@ describe('methods', () => {
         generationStrategy: mockGenerationStrategy,
         schema: v.any(),
         serialize: (id) => id.toString(),
-        deserialize: (id) => Number(id.toString()),
+        deserialize: (id) => Number(id?.toString() ?? 0),
       });
     ds = new JsonLinesDataSource<typeof schema>();
     ds.prepareResource(r);
@@ -133,7 +133,10 @@ describe('methods', () => {
           expect.any(String),
           toJsonl([
             ...dummyItems,
-            data
+            {
+              id: 0,
+              ...data,
+            }
           ])
         );
         expect(newItem).toEqual(data);
diff --git a/packages/examples/cms-web-api/bruno/Create Post with ID.bru b/packages/examples/cms-web-api/bruno/Create Post with ID.bru
new file mode 100644
index 0000000..9c5c5b8
--- /dev/null
+++ b/packages/examples/cms-web-api/bruno/Create Post with ID.bru	
@@ -0,0 +1,19 @@
+meta {
+  name: Create Post with ID
+  type: http
+  seq: 7
+}
+
+put {
+  url: http://localhost:6969/api/posts/5fac64d6-d261-42bb-a67b-bc7e1955a7e2
+  body: json
+  auth: none
+}
+
+body:json {
+  {
+    "title": "Emplaced Post",
+    "content": "Created post at ID",
+    "id": "5fac64d6-d261-42bb-a67b-bc7e1955a7e2"
+  }
+}
diff --git a/packages/examples/cms-web-api/bruno/Modify Post (Delta).bru b/packages/examples/cms-web-api/bruno/Modify Post (Delta).bru
index 7856344..09415ec 100644
--- a/packages/examples/cms-web-api/bruno/Modify Post (Delta).bru	
+++ b/packages/examples/cms-web-api/bruno/Modify Post (Delta).bru	
@@ -5,7 +5,7 @@ meta {
 }
 
 patch {
-  url: http://localhost:6969/api/posts/5fac64d6-d261-42bb-a67b-bc7e1955a7e2
+  url: http://localhost:6969/api/posts/9ba60691-0cd3-4e8a-9f44-e92b19fcacbc
   body: json
   auth: none
 }
diff --git a/packages/examples/cms-web-api/bruno/Modify Post (Merge).bru b/packages/examples/cms-web-api/bruno/Modify Post (Merge).bru
index 8e68d99..9ca2876 100644
--- a/packages/examples/cms-web-api/bruno/Modify Post (Merge).bru	
+++ b/packages/examples/cms-web-api/bruno/Modify Post (Merge).bru	
@@ -5,7 +5,7 @@ meta {
 }
 
 patch {
-  url: http://localhost:6969/api/posts/5fac64d6-d261-42bb-a67b-bc7e1955a7e2
+  url: http://localhost:6969/api/posts/9ba60691-0cd3-4e8a-9f44-e92b19fcacbc
   body: json
   auth: none
 }
diff --git a/packages/examples/cms-web-api/bruno/Replace Post.bru b/packages/examples/cms-web-api/bruno/Replace Post.bru
index 8cc6909..aef447e 100644
--- a/packages/examples/cms-web-api/bruno/Replace Post.bru	
+++ b/packages/examples/cms-web-api/bruno/Replace Post.bru	
@@ -1,11 +1,11 @@
 meta {
   name: Replace Post
   type: http
-  seq: 7
+  seq: 6
 }
 
 put {
-  url: http://localhost:6969/api/posts/5fac64d6-d261-42bb-a67b-bc7e1955a7e2
+  url: http://localhost:6969/api/posts/9ba60691-0cd3-4e8a-9f44-e92b19fcacbc
   body: json
   auth: none
 }
@@ -14,6 +14,6 @@ body:json {
   {
     "title": "Replaced Post",
     "content": "The old content is gone.",
-    "id": "5fac64d6-d261-42bb-a67b-bc7e1955a7e2"
+    "id": "9ba60691-0cd3-4e8a-9f44-e92b19fcacbc"
   }
 }
diff --git a/packages/examples/cms-web-api/src/index.ts b/packages/examples/cms-web-api/src/index.ts
index 9d5ba44..759a79c 100644
--- a/packages/examples/cms-web-api/src/index.ts
+++ b/packages/examples/cms-web-api/src/index.ts
@@ -25,14 +25,10 @@ const User = resource(
   .canPatch()
   .canDelete();
 
-const now = () => new Date();
-
 const Post = resource(
   v.object({
     title: v.string(),
     content: v.string(),
-    createdAt: v.optional(v.datelike(), now),
-    updatedAt: v.optional(v.datelike(), now),
   })
 )
   .name('Post')
@@ -43,6 +39,8 @@ const Post = resource(
     serialize: (v: unknown) => v?.toString() ?? '',
     deserialize: (v: string) => v,
   })
+  .createdAt('createdAt')
+  .updatedAt('updatedAt')
   .canFetchItem()
   .canFetchCollection()
   .canCreate()
@@ -58,7 +56,8 @@ const app = application({
 
 const backend = app.createBackend({
   dataSource: new JsonLinesDataSource(),
-});
+})
+  .throwsErrorOnDeletingNotFound();
 
 const server = backend.createHttpServer({
   basePath: '/api',