diff --git a/app/__test__/data/mutation.simple.test.ts b/app/__test__/data/mutation.simple.test.ts
index b54bca8..ac19935 100644
--- a/app/__test__/data/mutation.simple.test.ts
+++ b/app/__test__/data/mutation.simple.test.ts
@@ -186,7 +186,7 @@ describe("Mutator simple", async () => {
       const newCount = (await em.repo(items).count()).count;
       expect(newCount).toBe(oldCount + inserts.length);
 
-      const { data: data2 } = await em.repo(items).findMany();
+      const { data: data2 } = await em.repo(items).findMany({ offset: oldCount });
       expect(data2).toEqual(data);
    });
 });
diff --git a/app/__test__/data/prototype.test.ts b/app/__test__/data/prototype.test.ts
index f905775..8b12aa4 100644
--- a/app/__test__/data/prototype.test.ts
+++ b/app/__test__/data/prototype.test.ts
@@ -3,6 +3,7 @@ import {
    BooleanField,
    DateField,
    Entity,
+   EntityIndex,
    EntityManager,
    EnumField,
    JsonField,
@@ -278,23 +279,32 @@ describe("prototype", () => {
    test("schema", async () => {
       const _em = em(
          {
-            posts: entity("posts", { name: text() }),
-            comments: entity("comments", { some: text() })
+            posts: entity("posts", { name: text(), slug: text().required() }),
+            comments: entity("comments", { some: text() }),
+            users: entity("users", { email: text() })
          },
-         (relation, { posts, comments }) => {
-            relation(posts).manyToOne(comments);
+         ({ relation, index }, { posts, comments, users }) => {
+            relation(posts).manyToOne(comments).manyToOne(users);
+            index(posts).on(["name"]).on(["slug"], true);
          }
       );
 
       type LocalDb = (typeof _em)["DB"];
 
       const es = [
-         new Entity("posts", [new TextField("name")]),
-         new Entity("comments", [new TextField("some")])
+         new Entity("posts", [new TextField("name"), new TextField("slug", { required: true })]),
+         new Entity("comments", [new TextField("some")]),
+         new Entity("users", [new TextField("email")])
       ];
-      const _em2 = new EntityManager(es, new DummyConnection(), [
-         new ManyToOneRelation(es[0], es[1])
-      ]);
+      const _em2 = new EntityManager(
+         es,
+         new DummyConnection(),
+         [new ManyToOneRelation(es[0], es[1]), new ManyToOneRelation(es[0], es[2])],
+         [
+            new EntityIndex(es[0], [es[0].field("name")!]),
+            new EntityIndex(es[0], [es[0].field("slug")!], true)
+         ]
+      );
 
       // @ts-ignore
       expect(_em2.toJSON()).toEqual(_em.toJSON());
diff --git a/app/src/data/entities/Entity.ts b/app/src/data/entities/Entity.ts
index 0a285e7..579ffb2 100644
--- a/app/src/data/entities/Entity.ts
+++ b/app/src/data/entities/Entity.ts
@@ -220,7 +220,8 @@ export class Entity<
             readOnly: !field.isFillable("update") ? true : undefined,
             writeOnly: !field.isFillable("create") ? true : undefined,
             ...field.toJsonSchema()
-         }))
+         })),
+         { additionalProperties: false }
       );
 
       return clean ? JSON.parse(JSON.stringify(schema)) : schema;
diff --git a/app/src/data/fields/TextField.ts b/app/src/data/fields/TextField.ts
index 6314618..6dc17d3 100644
--- a/app/src/data/fields/TextField.ts
+++ b/app/src/data/fields/TextField.ts
@@ -104,6 +104,12 @@ export class TextField<Required extends true | false = false> extends Field<
          );
       }
 
+      if (this.config.pattern && value && !new RegExp(this.config.pattern).test(value)) {
+         throw new TransformPersistFailedException(
+            `Field "${this.name}" must match the pattern ${this.config.pattern}`
+         );
+      }
+
       return value;
    }
 
diff --git a/app/src/data/prototype/index.ts b/app/src/data/prototype/index.ts
index 37ca5b2..e9e868f 100644
--- a/app/src/data/prototype/index.ts
+++ b/app/src/data/prototype/index.ts
@@ -10,6 +10,7 @@ import {
    type DateFieldConfig,
    Entity,
    type EntityConfig,
+   EntityIndex,
    type EntityRelation,
    EnumField,
    type EnumFieldConfig,
@@ -244,47 +245,83 @@ export function relation<Local extends Entity>(local: Local) {
    };
 }
 
+export function index<E extends Entity>(entity: E) {
+   return {
+      on: (fields: (keyof InsertSchema<E>)[], unique?: boolean) => {
+         const _fields = fields.map((f) => {
+            const field = entity.field(f as any);
+            if (!field) {
+               throw new Error(`Field "${String(f)}" not found on entity "${entity.name}"`);
+            }
+            return field;
+         });
+         return new EntityIndex(entity, _fields, unique);
+      }
+   };
+}
+
 class EntityManagerPrototype<Entities extends Record<string, Entity>> extends EntityManager<
    Schema<Entities>
 > {
    constructor(
       public __entities: Entities,
-      relations: EntityRelation[]
+      relations: EntityRelation[] = [],
+      indices: EntityIndex[] = []
    ) {
-      super(Object.values(__entities), new DummyConnection(), relations);
+      super(Object.values(__entities), new DummyConnection(), relations, indices);
    }
 }
 
+type Chained<Fn extends (...args: any[]) => any, Rt = ReturnType<Fn>> = <E extends Entity>(
+   e: E
+) => {
+   [K in keyof Rt]: Rt[K] extends (...args: any[]) => any
+      ? (...args: Parameters<Rt[K]>) => Rt
+      : never;
+};
+
 export function em<Entities extends Record<string, Entity>>(
    entities: Entities,
-   schema?: (rel: typeof relation, entities: Entities) => void
+   schema?: (
+      fns: { relation: Chained<typeof relation>; index: Chained<typeof index> },
+      entities: Entities
+   ) => void
 ) {
    const relations: EntityRelation[] = [];
-   const relationProxy = (local: Entity) => {
-      return new Proxy(relation(local), {
+   const indices: EntityIndex[] = [];
+
+   const relationProxy = (e: Entity) => {
+      return new Proxy(relation(e), {
          get(target, prop) {
-            if (typeof target[prop] === "function") {
-               return (...args: any[]) => {
-                  const result = target[prop](...args);
-                  relations.push(result);
-                  return result;
-               };
-            }
-            return target[prop];
+            return (...args: any[]) => {
+               relations.push(target[prop](...args));
+               return relationProxy(e);
+            };
          }
-      });
+      }) as any;
+   };
+
+   const indexProxy = (e: Entity) => {
+      return new Proxy(index(e), {
+         get(target, prop) {
+            return (...args: any[]) => {
+               indices.push(target[prop](...args));
+               return indexProxy(e);
+            };
+         }
+      }) as any;
    };
 
    if (schema) {
-      schema(relationProxy, entities);
+      schema({ relation: relationProxy, index: indexProxy }, entities);
    }
 
-   const e = new EntityManagerPrototype(entities, relations);
+   const e = new EntityManagerPrototype(entities, relations, indices);
    return {
       DB: e.__entities as unknown as Schemas<Entities>,
       entities: e.__entities,
       relations,
-      indices: [],
+      indices,
       toJSON: () =>
          e.toJSON() as unknown as Pick<ModuleConfigs["data"], "entities" | "relations" | "indices">
    };