For some reason now it works properly.

NOTE: this solution is unstable and can change in the future.

package.json

@@ -9,10 +9,12 @@
     "lint": "next lint"
   },
   "dependencies": {
+    "lowdb": "^7.0.1",
     "match-sorter": "^8.0.0",
     "next": "15.2.4",
     "react": "^19.0.0",
     "react-dom": "^19.0.0",
+    "server-only": "^0.0.1",
     "sort-by": "^1.2.0",
     "tiny-invariant": "^1.3.3"
   },

pnpm-lock.yaml

@@ -8,6 +8,9 @@ importers:
 
   .:
     dependencies:
+      lowdb:
+        specifier: ^7.0.1
+        version: 7.0.1
       match-sorter:
         specifier: ^8.0.0
         version: 8.0.0
@@ -20,6 +23,9 @@ importers:
       react-dom:
         specifier: ^19.0.0
         version: 19.1.0(react@19.1.0)
+      server-only:
+        specifier: ^0.0.1
+        version: 0.0.1
       sort-by:
         specifier: ^1.2.0
         version: 1.2.0
@@ -1118,6 +1124,10 @@ packages:
     resolution: {integrity: sha512-lyuxPGr/Wfhrlem2CL/UcnUc1zcqKAImBDzukY7Y5F/yQiNdko6+fRLevlw1HgMySw7f611UIY408EtxRSoK3Q==}
     hasBin: true
 
+  lowdb@7.0.1:
+    resolution: {integrity: sha512-neJAj8GwF0e8EpycYIDFqEPcx9Qz4GUho20jWFR7YiFeXzF1YMLdxB36PypcTSPMA+4+LvgyMacYhlr18Zlymw==}
+    engines: {node: '>=18'}
+
   match-sorter@8.0.0:
     resolution: {integrity: sha512-bGJ6Zb+OhzXe+ptP5d80OLVx7AkqfRbtGEh30vNSfjNwllu+hHI+tcbMIT/fbkx/FKN1PmKuDb65+Oofg+XUxw==}
 
@@ -1348,6 +1358,9 @@ packages:
     engines: {node: '>=10'}
     hasBin: true
 
+  server-only@0.0.1:
+    resolution: {integrity: sha512-qepMx2JxAa5jjfzxG79yPPq+8BuFToHd1hm7kI+Z4zAq1ftQiP7HcxMhDDItrbtwVeLg/cY2JnKnrcFkmiswNA==}
+
   set-function-length@1.2.2:
     resolution: {integrity: sha512-pgRc4hJ4/sNjWCSS9AmnS40x3bNMDTknHgL5UaMBTMyJnU90EgWh1Rz+MC9eFu4BuN/UwZjKQuY/1v3rM7HMfg==}
     engines: {node: '>= 0.4'}
@@ -1401,6 +1414,10 @@ packages:
   stable-hash@0.0.5:
     resolution: {integrity: sha512-+L3ccpzibovGXFK+Ap/f8LOS0ahMrHTf3xu7mMLSpEGU0EO9ucaysSylKo9eRDFNhWve/y275iPmIZ4z39a9iA==}
 
+  steno@4.0.2:
+    resolution: {integrity: sha512-yhPIQXjrlt1xv7dyPQg2P17URmXbuM5pdGkpiMB3RenprfiBlvK415Lctfe0eshk90oA7/tNq7WEiMK8RSP39A==}
+    engines: {node: '>=18'}
+
   streamsearch@1.1.0:
     resolution: {integrity: sha512-Mcc5wHehp9aXz1ax6bZUyY5afg9u2rv5cqQI3mRrYkGC8rW2hM02jWuwjtL++LS5qinSyhj2QfLyNsuc+VsExg==}
     engines: {node: '>=10.0.0'}
@@ -2758,6 +2775,10 @@ snapshots:
     dependencies:
       js-tokens: 4.0.0
 
+  lowdb@7.0.1:
+    dependencies:
+      steno: 4.0.2
+
   match-sorter@8.0.0:
     dependencies:
       '@babel/runtime': 7.27.0
@@ -2996,6 +3017,8 @@ snapshots:
 
   semver@7.7.1: {}
 
+  server-only@0.0.1: {}
+
   set-function-length@1.2.2:
     dependencies:
       define-data-property: 1.1.4
@@ -3092,6 +3115,8 @@ snapshots:
 
   stable-hash@0.0.5: {}
 
+  steno@4.0.2: {}
+
   streamsearch@1.1.0: {}
 
   string.prototype.includes@2.0.1:

src/app/(sidebar)/contacts/[contactId]/edit/page.tsx

@@ -2,13 +2,22 @@ import Form from "next/form";
 import { fetchContact } from "@/app/(sidebar)/loaders";
 import { notFound, redirect } from "next/navigation";
 import { updateContact } from "@/app/data";
+import { revalidatePath } from "next/cache";
 
 
 async function editContact(contactId: string, formData: FormData) {
   "use server";
   const updates = Object.fromEntries(formData);
   await updateContact(contactId, updates);
-  redirect(`/contacts/${contactId}`);
+  revalidatePath('/(sidebar)', 'layout');  // THE NESTED BEHAVIOR IS UNSTABLE AND CAN CHANGE IN FUTURE.
+  redirect(`/contacts/${contactId}`);  // This makes the server component data be reloaded.
+  /*
+   * The server component architecture is a HTMX-like structure where the component rendered is STATE-LESS
+   * and that means that they don't automagically update.
+   * How do you say a server component to "re-render"? YOU REFRESH THE PAGE! THIS IS AS INTENDED!!!
+   * Do you want a component that re-render interactively from a "signal" client-side?
+   * That's a classical Client Component you dummy!! Go fetch clientside library and use that instead of Server Comps.
+   */
 }
 
 export default async function EditContactPage({

src/app/(sidebar)/contacts/[contactId]/page.tsx

@@ -1,6 +1,7 @@
 import { notFound } from "next/navigation";
 import Contact from "@/app/(sidebar)/contacts/[contactId]/Contact";
 import { fetchContact } from "@/app/(sidebar)/loaders";
+import React, { Suspense } from "react";
 
 export default async function ContactPage({
   params
@@ -14,6 +15,8 @@ export default async function ContactPage({
   });
 
   return (
+    <Suspense fallback={<div>Loading contact...</div>}>
       <Contact contact={contact}/>
+    </Suspense>
   );
 }

src/app/(sidebar)/layout.tsx

@@ -9,7 +9,7 @@ import { fetchContacts } from "@/app/(sidebar)/loaders";
 async function newContact() {
   "use server";
   await createEmptyContact();
-  revalidatePath('/');
+  revalidatePath('/(sidebar)', 'layout');
 }
 
 export default function SidebarRootLayout({

src/app/(sidebar)/loaders.ts

@@ -1,9 +1,13 @@
 import { getContact, getContacts } from "@/app/data";
 
+// This files is a non-needed interface file. I can directly call getContact/s into Server Components.
+
 export const fetchContacts = async () => {
+  console.log("fetch contacts");
   return await getContacts();
 };
 
 export const fetchContact = async (contactId: string) => {
+  console.log(`fetch contact ${contactId}`);
   return await getContact(contactId);
 };

src/app/data.ts

@@ -2,11 +2,16 @@
 // 🛑 Nothing in here has anything to do with React Router, it's just a fake database
 ////////////////////////////////////////////////////////////////////////////////
 // noinspection UnnecessaryLocalVariableJS,JSUnusedGlobalSymbols
+import "server-only";
 
 import { matchSorter } from "match-sorter";
 // @ts-expect-error - no types, but it's a tiny function
 import sortBy from "sort-by";
 import invariant from "tiny-invariant";
+import { Low } from "lowdb";
+import { JSONFile } from "lowdb/node";
+import { join } from "path";
+import { mkdir } from "fs/promises";
 
 type ContactMutation = {
   id?: string;
@@ -23,42 +28,97 @@ export type ContactRecord = ContactMutation & {
   createdAt: string;
 };
 
-////////////////////////////////////////////////////////////////////////////////
-// This is just a fake DB table. In a real app you'd be talking to a real db or
-// fetching from an existing API.
-const fakeContacts = {
-  records: {} as Record<string, ContactRecord>,
+// Define the database schema
+type Schema = {
+  records: Record<string, ContactRecord>;
+};
 
+// Set up lowdb
+const initDb = async (): Promise<Low<Schema>> => {
+  // Ensure the db directory exists
+  const dbDir = join(process.cwd(), '.db');
+  await mkdir(dbDir, { recursive: true });
+
+  const file = join(dbDir, 'contacts.json');
+  const adapter = new JSONFile<Schema>(file);
+  const defaultData: Schema = { records: {} };
+  const db = new Low<Schema>(adapter, defaultData);
+
+  // Load existing data
+  await db.read();
+
+  // Initialize if needed
+  if (!db.data) {
+    db.data = defaultData;
+  }
+
+  return db;
+};
+
+// Create a singleton instance of the database
+let dbPromise: Promise<Low<Schema>> | null = null;
+
+const getDb = () => {
+  if (!dbPromise) {
+    dbPromise = initDb();
+  }
+  return dbPromise;
+};
+
+////////////////////////////////////////////////////////////////////////////////
+// This is a DB wrapper using lowdb for persistence
+const fakeContacts = {
   async getAll(): Promise<ContactRecord[]> {
-    return Object.keys(fakeContacts.records)
-      .map((key) => fakeContacts.records[key])
+    const db = await getDb();
+    return Object.keys(db.data.records)
+      .map((key) => db.data.records[key])
       .sort(sortBy("-createdAt", "last"));
   },
 
   async get(id: string): Promise<ContactRecord | null> {
-    return fakeContacts.records[id] || null;
+    const db = await getDb();
+    return db.data.records[id] || null;
   },
 
   async create(values: ContactMutation): Promise<ContactRecord> {
+    const db = await getDb();
     const id = values.id || Math.random().toString(36).substring(2, 9);
     const createdAt = new Date().toISOString();
     const newContact = { id, createdAt, ...values };
-    fakeContacts.records[id] = newContact;
+    db.data.records[id] = newContact;
+    await db.write();
     return newContact;
   },
 
   async set(id: string, values: ContactMutation): Promise<ContactRecord> {
-    const contact = await fakeContacts.get(id);
+    const db = await getDb();
+    const contact = await this.get(id);
     invariant(contact, `No contact found for ${id}`);
     const updatedContact = { ...contact, ...values };
-    fakeContacts.records[id] = updatedContact;
+    db.data.records[id] = updatedContact;
+    await db.write();
     return updatedContact;
   },
 
-  destroy(id: string): null {
-    delete fakeContacts.records[id];
+  async destroy(id: string): Promise<null> {
+    const db = await getDb();
+    delete db.data.records[id];
+    await db.write();
     return null;
   },
+
+  // New reset function to restore the initial data
+  async reset(): Promise<void> {
+    const db = await getDb();
+    db.data.records = {};
+    await db.write();
+
+    // Restore initial data
+    const initialContacts = getInitialContacts();
+    for (const contact of initialContacts) {
+      await this.create(contact);
+    }
+  }
 };
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -93,10 +153,18 @@ export async function updateContact(id: string, updates: ContactMutation) {
 }
 
 export async function deleteContact(id: string) {
-  fakeContacts.destroy(id);
+  await fakeContacts.destroy(id);
 }
 
-[
+// New function to reset the database to initial state
+export async function resetDatabase() {
+  console.log("RESET DATABASE");
+  await fakeContacts.reset();
+}
+
+// Helper function to get initial contacts data
+function getInitialContacts() {
+  return [
     {
       avatar:
         "https://sessionize.com/image/124e-400o400o2-wHVdAuNaxi8KJrgtN3ZKci.jpg",
@@ -309,12 +377,19 @@ export async function deleteContact(id: string) {
       last: "Jensen",
       twitter: "@jenseng",
     },
-].forEach((contact) => {
-  fakeContacts.create({
+  ].map(contact => ({
     ...contact,
     id: `${contact.first
       .toLowerCase()
       .split(" ")
-      .join("_")}-${contact.last.toLocaleLowerCase()}`,
-  });
-});
+      .join("_")}-${contact.last.toLowerCase()}`,
+  }));
+}
+
+// Initialize with seed data on first load
+(async () => {
+  const db = await getDb();
+  if (Object.keys(db.data.records).length === 0) {
+    await resetDatabase();
+  }
+})();