Digital Savings Vault

Learn how to build a digital savings vault application using Yabetoo, inspired by platforms like SafeLock. This guide covers vault creation, deposits, scheduled unlocks, and withdrawal processing.

Overview

Digital savings platforms need to handle:

Goal-based savings vaults with lock periods
Mobile money deposits
Automatic and manual vault unlocks
Withdrawal processing with fees
Interest or rewards calculations
Multi-vault management per user

How SafeLock Works

SafeLock is a mobile-first financial management app that helps users save money through “vaults” - locked savings containers tied to personal goals with predetermined release dates. Key features include:

Goal Tracking: Multiple vaults for different objectives
Mobile Money Integration: MTN and Airtel Money support
Flexible Unlocking: Auto-unlock at maturity or early withdrawal with fees
Offline Support: Access accounts without internet

Architecture

Implementation

1. Data Models

Define vault and transaction structures:

// types.ts
interface User {
  id: string;
  firstName: string;
  lastName: string;
  phone: string;
  operatorName: 'mtn' | 'airtel';
  email?: string;
  totalSavings: number;
  createdAt: Date;
}

interface Vault {
  id: string;
  userId: string;
  name: string;
  goal: string;
  targetAmount: number;
  currentAmount: number;
  currency: string;
  unlockDate: Date;
  status: 'active' | 'matured' | 'withdrawn' | 'cancelled';
  autoWithdraw: boolean;
  createdAt: Date;
  unlockedAt?: Date;
  withdrawnAt?: Date;
}

interface VaultTransaction {
  id: string;
  vaultId: string;
  userId: string;
  type: 'deposit' | 'withdrawal' | 'early_withdrawal' | 'interest';
  amount: number;
  fee: number;
  netAmount: number;
  paymentIntentId?: string;
  disbursementId?: string;
  status: 'pending' | 'completed' | 'failed';
  createdAt: Date;
}

// Fee configuration
const FEES = {
  EARLY_WITHDRAWAL_PERCENT: 3,  // 3% fee for early withdrawal
  MATURITY_WITHDRAWAL_PERCENT: 0, // No fee at maturity
  MINIMUM_DEPOSIT: 500,  // 500 XAF minimum
  MINIMUM_VAULT_PERIOD_DAYS: 7  // Minimum 7 days lock
};

2. Create Savings Vault

Allow users to create goal-based vaults:

import Yabetoo from '@yabetoo/sdk-js';

const yabetoo = new Yabetoo(process.env.YABETOO_SECRET_KEY!);

async function createVault(
  userId: string,
  vaultData: {
    name: string;
    goal: string;
    targetAmount: number;
    unlockDate: Date;
    autoWithdraw: boolean;
    initialDeposit?: number;
  }
) {
  const user = await db.users.findById(userId);

  // Validate unlock date
  const minUnlockDate = new Date();
  minUnlockDate.setDate(minUnlockDate.getDate() + FEES.MINIMUM_VAULT_PERIOD_DAYS);

  if (vaultData.unlockDate < minUnlockDate) {
    throw new Error(`Vault must be locked for at least ${FEES.MINIMUM_VAULT_PERIOD_DAYS} days`);
  }

  // Create vault
  const vault: Vault = {
    id: generateVaultId(),
    userId,
    name: vaultData.name,
    goal: vaultData.goal,
    targetAmount: vaultData.targetAmount,
    currentAmount: 0,
    currency: 'XAF',
    unlockDate: vaultData.unlockDate,
    status: 'active',
    autoWithdraw: vaultData.autoWithdraw,
    createdAt: new Date()
  };

  await db.vaults.create(vault);

  // Handle initial deposit if provided
  let paymentIntent = null;
  if (vaultData.initialDeposit && vaultData.initialDeposit >= FEES.MINIMUM_DEPOSIT) {
    paymentIntent = await createDeposit(vault.id, vaultData.initialDeposit);
  }

  return { vault, paymentIntent };
}

3. Deposit to Vault

Process deposits via mobile money:

async function createDeposit(vaultId: string, amount: number) {
  if (amount < FEES.MINIMUM_DEPOSIT) {
    throw new Error(`Minimum deposit is ${FEES.MINIMUM_DEPOSIT} XAF`);
  }

  const vault = await db.vaults.findById(vaultId);
  if (!vault) throw new Error('Vault not found');
  if (vault.status !== 'active') throw new Error('Vault is not active');

  const user = await db.users.findById(vault.userId);

  // Create payment intent
  const intent = await yabetoo.payments.create({
    amount,
    currency: 'XAF',
    description: `Deposit to ${vault.name}`,
    metadata: {
      vaultId,
      userId: vault.userId,
      vaultName: vault.name,
      type: 'vault_deposit'
    }
  });

  // Create pending transaction
  await db.vaultTransactions.create({
    id: generateTransactionId(),
    vaultId,
    userId: vault.userId,
    type: 'deposit',
    amount,
    fee: 0,
    netAmount: amount,
    paymentIntentId: intent.id,
    status: 'pending',
    createdAt: new Date()
  });

  return intent;
}

async function confirmDeposit(
  paymentIntentId: string,
  paymentMethod: {
    phone: string;
    operatorName: 'mtn' | 'airtel';
  }
) {
  const transaction = await db.vaultTransactions.findByPaymentIntent(paymentIntentId);
  const vault = await db.vaults.findById(transaction.vaultId);
  const user = await db.users.findById(vault.userId);

  const confirmation = await yabetoo.payments.confirm(paymentIntentId, {
    clientSecret: transaction.clientSecret,
    firstName: user.firstName,
    lastName: user.lastName,
    paymentMethodData: {
      type: 'momo',
      momo: {
        msisdn: paymentMethod.phone,
        country: 'cg',
        operatorName: paymentMethod.operatorName
      }
    }
  });

  return confirmation;
}

4. Webhook Handler for Deposits

Process successful deposits:

app.post('/webhooks/yabetoo', async (req, res) => {
  const event = req.body;

  switch (event.type) {
    case 'payment_intent.succeeded':
      if (event.data.metadata.type === 'vault_deposit') {
        await handleDepositSuccess(event.data);
      }
      break;

    case 'payment_intent.failed':
      if (event.data.metadata.type === 'vault_deposit') {
        await handleDepositFailure(event.data);
      }
      break;

    case 'disbursement.completed':
      if (event.data.metadata?.type === 'vault_withdrawal') {
        await handleWithdrawalComplete(event.data);
      }
      break;
  }

  res.json({ received: true });
});

async function handleDepositSuccess(data: any) {
  const { vaultId, userId } = data.metadata;
  const amount = data.amount;

  // Update transaction
  await db.vaultTransactions.updateByPaymentIntent(data.id, {
    status: 'completed'
  });

  // Update vault balance
  await db.vaults.incrementAmount(vaultId, amount);

  // Update user total savings
  await db.users.incrementTotalSavings(userId, amount);

  // Get updated vault
  const vault = await db.vaults.findById(vaultId);

  // Send notification
  await sendNotification(userId, {
    type: 'deposit_success',
    title: 'Deposit Successful',
    message: `${amount} XAF has been added to your "${vault.name}" vault. New balance: ${vault.currentAmount} XAF`,
    vaultId
  });

  // Check if target reached
  if (vault.currentAmount >= vault.targetAmount) {
    await sendNotification(userId, {
      type: 'target_reached',
      title: 'Goal Reached! 🎉',
      message: `Congratulations! You've reached your savings goal for "${vault.name}"!`,
      vaultId
    });
  }
}

5. Vault Maturity Processing

Handle vault unlocks when maturity date is reached:

// Run daily via cron job
async function processMaturedVaults() {
  const maturedVaults = await db.vaults.findMany({
    where: {
      status: 'active',
      unlockDate: { lte: new Date() }
    }
  });

  for (const vault of maturedVaults) {
    try {
      // Update vault status
      await db.vaults.update(vault.id, {
        status: 'matured',
        unlockedAt: new Date()
      });

      const user = await db.users.findById(vault.userId);

      // Notify user
      await sendNotification(vault.userId, {
        type: 'vault_matured',
        title: 'Vault Unlocked! 🔓',
        message: `Your "${vault.name}" vault is now unlocked! You can withdraw ${vault.currentAmount} XAF without any fees.`,
        vaultId: vault.id
      });

      // Process auto-withdrawal if enabled
      if (vault.autoWithdraw && vault.currentAmount > 0) {
        await processWithdrawal(vault.id, vault.currentAmount, false);
      }

    } catch (error) {
      console.error(`Failed to process matured vault ${vault.id}:`, error);
      await notifyAdminOfVaultError(vault.id, error);
    }
  }
}

6. Withdrawal Processing

Handle both maturity and early withdrawals:

async function processWithdrawal(
  vaultId: string,
  amount: number,
  isEarly: boolean = false
) {
  const vault = await db.vaults.findById(vaultId);
  const user = await db.users.findById(vault.userId);

  if (amount > vault.currentAmount) {
    throw new Error('Insufficient vault balance');
  }

  // Check if early withdrawal
  const now = new Date();
  if (vault.status === 'active' && now < vault.unlockDate) {
    isEarly = true;
  }

  // Calculate fee
  const feePercent = isEarly
    ? FEES.EARLY_WITHDRAWAL_PERCENT
    : FEES.MATURITY_WITHDRAWAL_PERCENT;
  const fee = Math.round(amount * (feePercent / 100));
  const netAmount = amount - fee;

  // Create withdrawal transaction
  const transaction: VaultTransaction = {
    id: generateTransactionId(),
    vaultId,
    userId: vault.userId,
    type: isEarly ? 'early_withdrawal' : 'withdrawal',
    amount,
    fee,
    netAmount,
    status: 'pending',
    createdAt: new Date()
  };

  await db.vaultTransactions.create(transaction);

  // Process disbursement
  const disbursement = await yabetoo.disbursements.create({
    amount: netAmount,
    currency: 'XAF',
    firstName: user.firstName,
    lastName: user.lastName,
    paymentMethodData: {
      type: 'momo',
      momo: {
        msisdn: user.phone,
        country: 'cg',
        operatorName: user.operatorName
      }
    }
  });

  // Update transaction with disbursement ID
  await db.vaultTransactions.update(transaction.id, {
    disbursementId: disbursement.id
  });

  // Update vault
  await db.vaults.update(vaultId, {
    currentAmount: vault.currentAmount - amount,
    status: vault.currentAmount - amount === 0 ? 'withdrawn' : vault.status,
    withdrawnAt: vault.currentAmount - amount === 0 ? new Date() : undefined
  });

  // Update user total savings
  await db.users.decrementTotalSavings(vault.userId, amount);

  return { transaction, disbursement, fee, netAmount };
}

7. Dashboard Statistics

Provide users with savings insights:

async function getUserDashboard(userId: string) {
  const user = await db.users.findById(userId);
  const vaults = await db.vaults.findByUser(userId);
  const transactions = await db.vaultTransactions.findByUser(userId);

  const activeVaults = vaults.filter(v => v.status === 'active');
  const maturedVaults = vaults.filter(v => v.status === 'matured');

  // Calculate statistics
  const totalDeposits = transactions
    .filter(t => t.type === 'deposit' && t.status === 'completed')
    .reduce((sum, t) => sum + t.amount, 0);

  const totalWithdrawals = transactions
    .filter(t => ['withdrawal', 'early_withdrawal'].includes(t.type) && t.status === 'completed')
    .reduce((sum, t) => sum + t.amount, 0);

  const totalFeesPaid = transactions
    .filter(t => t.status === 'completed')
    .reduce((sum, t) => sum + t.fee, 0);

  // Upcoming unlocks
  const upcomingUnlocks = activeVaults
    .filter(v => v.unlockDate > new Date())
    .sort((a, b) => a.unlockDate.getTime() - b.unlockDate.getTime())
    .slice(0, 5);

  // Progress towards goals
  const vaultProgress = activeVaults.map(vault => ({
    vaultId: vault.id,
    name: vault.name,
    goal: vault.goal,
    currentAmount: vault.currentAmount,
    targetAmount: vault.targetAmount,
    progressPercent: Math.round((vault.currentAmount / vault.targetAmount) * 100),
    daysUntilUnlock: Math.ceil(
      (vault.unlockDate.getTime() - Date.now()) / (1000 * 60 * 60 * 24)
    )
  }));

  return {
    summary: {
      totalSavings: user.totalSavings,
      activeVaults: activeVaults.length,
      maturedVaults: maturedVaults.length,
      totalDeposits,
      totalWithdrawals,
      totalFeesPaid
    },
    vaultProgress,
    upcomingUnlocks,
    recentTransactions: transactions.slice(0, 10)
  };
}

8. Savings Reminders

Encourage regular deposits:

// Run weekly via cron job
async function sendSavingsReminders() {
  const users = await db.users.findAll();

  for (const user of users) {
    const activeVaults = await db.vaults.findActiveByUser(user.id);

    if (activeVaults.length === 0) continue;

    // Check for vaults below target with approaching unlock dates
    const urgentVaults = activeVaults.filter(vault => {
      const daysUntilUnlock = Math.ceil(
        (vault.unlockDate.getTime() - Date.now()) / (1000 * 60 * 60 * 24)
      );
      const progressPercent = (vault.currentAmount / vault.targetAmount) * 100;

      return daysUntilUnlock <= 30 && progressPercent < 80;
    });

    if (urgentVaults.length > 0) {
      for (const vault of urgentVaults) {
        const remaining = vault.targetAmount - vault.currentAmount;
        const daysLeft = Math.ceil(
          (vault.unlockDate.getTime() - Date.now()) / (1000 * 60 * 60 * 24)
        );

        await sendNotification(user.id, {
          type: 'savings_reminder',
          title: 'Savings Reminder 💰',
          message: `Your "${vault.name}" vault needs ${remaining} XAF more to reach your goal. You have ${daysLeft} days left!`,
          vaultId: vault.id
        });
      }
    }
  }
}

User Flow

Create Account

User registers with phone number (MTN or Airtel).

Create Vault

User creates a savings vault with a goal, target amount, and unlock date.

Make Deposits

User deposits money via mobile money at any time.

Track Progress

User monitors progress towards savings goals in the app.

Vault Matures

When unlock date arrives, vault becomes available for withdrawal.

Withdraw

User withdraws funds to their mobile money account.

Fee Structure

Action	Fee
Deposit	Free
Withdrawal at maturity	Free
Early withdrawal	3%
Account maintenance	Free

Best Practices

Savings Challenges

Create weekly or monthly savings challenges to encourage consistent deposits.

Social Features

Flexible Goals

Let users adjust target amounts and dates if circumstances change.

Interest/Rewards

Consider offering small rewards for completing savings goals on time.

Notification Templates

const NOTIFICATION_TEMPLATES = {
  deposit_success: (amount: number, vaultName: string, balance: number) =>
    `✅ ${amount} XAF deposited to "${vaultName}". Balance: ${balance} XAF`,

  vault_matured: (vaultName: string, amount: number) =>
    `🔓 Your "${vaultName}" vault is unlocked! Withdraw ${amount} XAF fee-free.`,

  target_reached: (vaultName: string) =>
    `🎉 Goal reached for "${vaultName}"! Keep saving or wait for unlock.`,

  savings_reminder: (vaultName: string, remaining: number, days: number) =>
    `💰 "${vaultName}" needs ${remaining} XAF in ${days} days. Deposit now!`,

  early_withdrawal: (amount: number, fee: number, received: number) =>
    `⚠️ Early withdrawal: ${amount} XAF - ${fee} XAF fee = ${received} XAF sent.`
};

Payment Intents

Learn about processing deposits

Disbursements

Handle withdrawals to users

Overview

Platform Integrations

Case Studies

Overview

How SafeLock Works

Architecture

Implementation

1. Data Models

2. Create Savings Vault

3. Deposit to Vault

4. Webhook Handler for Deposits

5. Vault Maturity Processing

6. Withdrawal Processing

7. Dashboard Statistics

8. Savings Reminders

User Flow

Fee Structure

Best Practices

Notification Templates

Payment Intents

Disbursements

Overview

Platform Integrations

Case Studies

​Overview

​How SafeLock Works

​Architecture

​Implementation

​1. Data Models

​2. Create Savings Vault

​3. Deposit to Vault

​4. Webhook Handler for Deposits

​5. Vault Maturity Processing

​6. Withdrawal Processing

​7. Dashboard Statistics

​8. Savings Reminders

​User Flow

​Fee Structure

​Best Practices

​Notification Templates

​Related Resources

Payment Intents

Disbursements

Overview

How SafeLock Works

Architecture

Implementation

1. Data Models

2. Create Savings Vault

3. Deposit to Vault

4. Webhook Handler for Deposits

5. Vault Maturity Processing

6. Withdrawal Processing

7. Dashboard Statistics

8. Savings Reminders

User Flow

Fee Structure

Best Practices

Notification Templates

Related Resources