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Preview
Preview Feature — This feature is currently in preview and under active development. APIs and functionality may change. We recommend testing thoroughly before using in production.

Examples

Real-world feature patterns using the code-first API. For conditionals, loops, and switch (e.g. branchOverrides, recordInput, recordScenarios), see Building Features - Conditionals, loops, and switch.

E-Commerce Order Fulfillment​

A complete order processing feature with payment, inventory, and notifications. Because the handler returns early when validation fails, use branchOverrides so the compiler records the payment and later steps; at runtime those steps run only when the condition holds.

await ductape.features.define({
  tag: 'order-fulfillment',
  name: 'Order Fulfillment',
  description: 'Process customer orders from payment to delivery',

  options: {
    timeout: 600000, // 10 minutes
    rollback_strategy: 'reverse_all',
  },

  signals: {
    'cancel-order': { input: { reason: 'string' } },
  },

  branchOverrides: { 'validate-order': { available: true } },

  handler: async (ctx) => {
    ctx.log.info('Starting order fulfillment', { orderId: ctx.input.orderId });

    // Step 1: Validate order and check inventory
    const validation = await ctx.step('validate-order', async () => {
      const inventory = await ctx.api.run({
        app: 'inventory-api',
        event: 'check-availability',
        input: { body: { items: ctx.input.items } },
      });

      return {
        available: inventory.allAvailable,
        unavailableItems: inventory.unavailableItems || [],
      };
    });

    if (!validation.available) {
      return {
        success: false,
        reason: 'items_unavailable',
        unavailableItems: validation.unavailableItems,
      };
    }

    // Step 2: Calculate totals and apply discounts
    const pricing = await ctx.step('calculate-pricing', async () => {
      const subtotal = ctx.input.items.reduce(
        (sum, item) => sum + item.price * item.quantity,
        0
      );

      let discount = 0;
      if (ctx.input.couponCode) {
        const coupon = await ctx.api.run({
          app: 'promotions-api',
          event: 'validate-coupon',
          input: { body: { code: ctx.input.couponCode } },
        });
        if (coupon.valid) {
          discount = coupon.discountAmount;
        }
      }

      const tax = (subtotal - discount) * 0.08; // 8% tax
      const total = subtotal - discount + tax;

      return { subtotal, discount, tax, total };
    });

    // Step 3: Process payment (with rollback)
    const payment = await ctx.step(
      'process-payment',
      async () => {
        return ctx.api.run({
          app: 'stripe',
          event: 'create-charge',
          input: {
            body: {
              amount: Math.round(pricing.total * 100), // cents
              currency: 'usd',
              customer: ctx.input.customerId,
              metadata: { orderId: ctx.input.orderId },
            },
            headers: {
              'Idempotency-Key': `order-${ctx.input.orderId}-payment`,
            },
          },
          retries: 3,
          timeout: 30000,
        });
      },
      async (result) => {
        // Rollback: Refund the charge
        await ctx.api.run({
          app: 'stripe',
          event: 'create-refund',
          input: {
            body: { charge: result.id, reason: 'order_cancelled' },
          },
        });
        ctx.log.info('Payment refunded', { chargeId: result.id });
      }
    );

    // Checkpoint after payment
    await ctx.checkpoint('payment-complete', {
      chargeId: payment.id,
      amount: pricing.total,
    });

    // Step 4: Reserve inventory (with rollback)
    await ctx.step(
      'reserve-inventory',
      async () => {
        return ctx.api.run({
          app: 'inventory-api',
          event: 'reserve-items',
          input: {
            body: {
              orderId: ctx.input.orderId,
              items: ctx.input.items,
            },
          },
        });
      },
      async () => {
        // Rollback: Release reserved items
        await ctx.api.run({
          app: 'inventory-api',
          event: 'release-items',
          input: { body: { orderId: ctx.input.orderId } },
        });
      }
    );

    // Step 5: Create order record
    const order = await ctx.step('create-order-record', async () => {
      return ctx.database.insert({
        database: 'orders-db',
        event: 'create-order',
        data: {
          order_id: ctx.input.orderId,
          customer_id: ctx.input.customerId,
          items: ctx.input.items,
          subtotal: pricing.subtotal,
          discount: pricing.discount,
          tax: pricing.tax,
          total: pricing.total,
          payment_id: payment.id,
          status: 'confirmed',
          created_at: new Date().toISOString(),
        },
      });
    });

    // Step 6: Send confirmation email (non-critical)
    await ctx.step(
      'send-confirmation-email',
      async () => {
        await ctx.notification.email({
          notification: 'transactional',
          event: 'order-confirmed',
          recipients: [ctx.input.email],
          subject: { orderId: ctx.input.orderId },
          template: {
            orderId: ctx.input.orderId,
            items: ctx.input.items,
            total: pricing.total,
            estimatedDelivery: '3-5 business days',
          },
        });
      },
      null,
      { allow_fail: true }
    );

    // Step 7: Queue for warehouse fulfillment
    await ctx.step('queue-fulfillment', async () => {
      await ctx.messaging.produce({
        event: 'warehouse-events:new-order',
        message: {
          orderId: ctx.input.orderId,
          items: ctx.input.items,
          shippingAddress: ctx.input.shippingAddress,
          priority: ctx.input.isPrime ? 'high' : 'normal',
        },
      });
    });

    ctx.log.info('Order fulfilled successfully', {
      orderId: ctx.input.orderId,
      chargeId: payment.id,
    });

    return {
      success: true,
      orderId: ctx.input.orderId,
      orderRecordId: order.id,
      chargeId: payment.id,
      total: pricing.total,
    };
  },
});

User Onboarding​

Multi-step user registration with email verification:

await ductape.features.define({
  tag: 'user-onboarding',
  name: 'User Onboarding',

  signals: {
    'email-verified': { input: { code: 'string' } },
  },

  handler: async (ctx) => {
    // Step 1: Create user account
    const user = await ctx.step(
      'create-user',
      async () => {
        return ctx.database.insert({
          database: 'users-db',
          event: 'create-user',
          data: {
            email: ctx.input.email,
            name: ctx.input.name,
            password_hash: ctx.input.passwordHash,
            status: 'pending_verification',
            created_at: new Date().toISOString(),
          },
        });
      },
      async (result) => {
        // Rollback: Delete user if onboarding fails
        await ctx.database.delete({
          database: 'users-db',
          event: 'delete-user',
          where: { id: result.id },
        });
      }
    );

    // Step 2: Generate verification code
    const verificationCode = Math.random().toString(36).substring(2, 8).toUpperCase();
    ctx.setState('verificationCode', verificationCode);

    // Step 3: Send verification email
    await ctx.step('send-verification', async () => {
      await ctx.notification.email({
        notification: 'transactional',
        event: 'email-verification',
        recipients: [ctx.input.email],
        subject: { appName: 'MyApp' },
        template: {
          name: ctx.input.name,
          code: verificationCode,
          expiresIn: '24 hours',
        },
      });
    });

    // Step 4: Wait for email verification
    const verification = await ctx.waitForSignal('email-verified', {
      timeout: '24h',
    });

    // Validate the code
    if (verification.code !== ctx.getState('verificationCode')) {
      await ctx.triggerRollback('Invalid verification code');
      return { success: false, reason: 'invalid_code' };
    }

    // Step 5: Activate user account
    await ctx.step('activate-user', async () => {
      await ctx.database.update({
        database: 'users-db',
        event: 'update-user',
        where: { id: user.id },
        data: {
          status: 'active',
          verified_at: new Date().toISOString(),
        },
      });
    });

    // Step 6: Create user profile
    await ctx.step('create-profile', async () => {
      await ctx.database.insert({
        database: 'profiles-db',
        event: 'create-profile',
        data: {
          user_id: user.id,
          display_name: ctx.input.name,
          avatar_url: null,
          bio: null,
        },
      });
    });

    // Step 7: Send welcome email (non-critical)
    await ctx.step(
      'send-welcome',
      async () => {
        await ctx.notification.email({
          notification: 'transactional',
          event: 'welcome',
          recipients: [ctx.input.email],
          template: {
            name: ctx.input.name,
            loginUrl: 'https://myapp.com/login',
          },
        });
      },
      null,
      { allow_fail: true }
    );

    return {
      success: true,
      userId: user.id,
      email: ctx.input.email,
    };
  },
});

Document Processing Pipeline​

Process uploaded documents with OCR and classification:

await ductape.features.define({
  tag: 'document-pipeline',
  name: 'Document Processing Pipeline',

  options: {
    timeout: 300000, // 5 minutes for large documents
  },

  handler: async (ctx) => {
    ctx.log.info('Processing document', {
      documentId: ctx.input.documentId,
      fileName: ctx.input.fileName,
    });

    // Step 1: Download the document
    const document = await ctx.step('download-document', async () => {
      return ctx.storage.download({
        storage: 'uploads',
        event: 'get-document',
        input: { file_key: ctx.input.fileKey },
      });
    });

    // Step 2: Run OCR extraction
    const ocrResult = await ctx.step(
      'extract-text',
      async () => {
        return ctx.api.run({
          app: 'ocr-service',
          event: 'extract',
          input: {
            body: {
              content: document.content,
              contentType: document.content_type,
              options: { language: 'en', detectLayout: true },
            },
          },
          timeout: 60000,
        });
      },
      null,
      { retries: 2 }
    );

    // Step 3: Classify document type
    const classification = await ctx.step('classify-document', async () => {
      return ctx.api.run({
        app: 'ml-classifier',
        event: 'classify',
        input: {
          body: {
            text: ocrResult.text,
            categories: ['invoice', 'receipt', 'contract', 'report', 'other'],
          },
        },
      });
    });

    // Step 4: Extract structured data based on document type
    const extractedData = await ctx.step('extract-data', async () => {
      const extractionConfig = {
        invoice: { fields: ['vendor', 'total', 'date', 'items'] },
        receipt: { fields: ['store', 'total', 'date', 'items'] },
        contract: { fields: ['parties', 'terms', 'date', 'signatures'] },
        report: { fields: ['title', 'author', 'date', 'summary'] },
        other: { fields: ['title', 'content'] },
      };

      return ctx.api.run({
        app: 'data-extractor',
        event: 'extract',
        input: {
          body: {
            text: ocrResult.text,
            documentType: classification.category,
            fields: extractionConfig[classification.category],
          },
        },
      });
    });

    // Step 5: Store processed document
    const processedDoc = await ctx.step('store-result', async () => {
      return ctx.database.insert({
        database: 'documents-db',
        event: 'store-processed',
        data: {
          original_file_key: ctx.input.fileKey,
          file_name: ctx.input.fileName,
          document_type: classification.category,
          confidence: classification.confidence,
          extracted_text: ocrResult.text,
          extracted_data: extractedData,
          processed_at: new Date().toISOString(),
        },
      });
    });

    // Step 6: Index for search
    await ctx.step(
      'index-document',
      async () => {
        await ctx.api.run({
          app: 'search-api',
          event: 'index',
          input: {
            body: {
              id: processedDoc.id,
              content: ocrResult.text,
              metadata: {
                type: classification.category,
                fileName: ctx.input.fileName,
                ...extractedData,
              },
            },
          },
        });
      },
      null,
      { allow_fail: true }
    );

    // Step 7: Notify user
    await ctx.step(
      'notify-completion',
      async () => {
        await ctx.notification.push({
          notification: 'app-notifications',
          event: 'document-processed',
          tokens: [ctx.input.deviceToken],
          title: { fileName: ctx.input.fileName },
          body: { documentType: classification.category },
          data: { documentId: processedDoc.id },
        });
      },
      null,
      { allow_fail: true }
    );

    return {
      success: true,
      documentId: processedDoc.id,
      documentType: classification.category,
      confidence: classification.confidence,
    };
  },
});

Subscription Billing​

Recurring subscription billing with retry logic:

await ductape.features.define({
  tag: 'subscription-billing',
  name: 'Subscription Billing',

  options: {
    rollback_strategy: 'critical_only',
  },

  handler: async (ctx) => {
    const { subscriptionId, customerId, amount } = ctx.input;

    ctx.log.info('Processing subscription billing', { subscriptionId });

    // Step 1: Get subscription details
    const subscription = await ctx.step('get-subscription', async () => {
      return ctx.database.query({
        database: 'subscriptions-db',
        event: 'get-subscription',
        params: { id: subscriptionId },
      });
    });

    if (!subscription || subscription.status !== 'active') {
      return { success: false, reason: 'subscription_inactive' };
    }

    // Step 2: Get payment method
    const paymentMethod = await ctx.step('get-payment-method', async () => {
      return ctx.api.run({
        app: 'stripe',
        event: 'get-payment-method',
        input: { params: { customerId } },
      });
    });

    if (!paymentMethod.valid) {
      // Notify about payment method issue
      await ctx.step(
        'notify-payment-issue',
        async () => {
          await ctx.notification.email({
            notification: 'billing',
            event: 'payment-method-invalid',
            recipients: [subscription.email],
            template: { updateUrl: 'https://app.com/billing' },
          });
        },
        null,
        { allow_fail: true }
      );

      return { success: false, reason: 'invalid_payment_method' };
    }

    // Step 3: Attempt payment (with retries)
    let paymentAttempt = 0;
    let paymentResult = null;
    let lastError = null;

    while (paymentAttempt < 3 && !paymentResult) {
      paymentAttempt++;
      ctx.setState('paymentAttempt', paymentAttempt);

      try {
        paymentResult = await ctx.step(`payment-attempt-${paymentAttempt}`, async () => {
          return ctx.api.run({
            app: 'stripe',
            event: 'create-charge',
            input: {
              body: {
                amount: amount * 100,
                currency: 'usd',
                customer: customerId,
                payment_method: paymentMethod.id,
                metadata: {
                  subscriptionId,
                  attempt: paymentAttempt,
                },
              },
              headers: {
                'Idempotency-Key': `sub-${subscriptionId}-${ctx.feature_id}-${paymentAttempt}`,
              },
            },
          });
        });
      } catch (error) {
        lastError = error;
        ctx.log.warn('Payment attempt failed', {
          attempt: paymentAttempt,
          error: error.message,
        });

        if (paymentAttempt < 3) {
          // Wait before retry (exponential backoff)
          await ctx.sleep(paymentAttempt * 2000);
        }
      }
    }

    if (!paymentResult) {
      // All payment attempts failed
      await ctx.step('mark-payment-failed', async () => {
        await ctx.database.update({
          database: 'subscriptions-db',
          event: 'update-subscription',
          where: { id: subscriptionId },
          data: {
            status: 'past_due',
            failed_payments: (subscription.failed_payments || 0) + 1,
            last_payment_error: lastError?.message,
          },
        });
      });

      await ctx.step(
        'notify-payment-failed',
        async () => {
          await ctx.notification.email({
            notification: 'billing',
            event: 'payment-failed',
            recipients: [subscription.email],
            template: {
              amount,
              attempts: paymentAttempt,
              updateUrl: 'https://app.com/billing',
            },
          });
        },
        null,
        { allow_fail: true }
      );

      return {
        success: false,
        reason: 'payment_failed',
        attempts: paymentAttempt,
      };
    }

    // Step 4: Record successful payment (critical)
    await ctx.step(
      'record-payment',
      async () => {
        return ctx.database.insert({
          database: 'payments-db',
          event: 'create-payment',
          data: {
            subscription_id: subscriptionId,
            customer_id: customerId,
            charge_id: paymentResult.id,
            amount,
            status: 'succeeded',
            created_at: new Date().toISOString(),
          },
        });
      },
      null,
      { critical: true }
    );

    // Step 5: Update subscription
    await ctx.step('update-subscription', async () => {
      await ctx.database.update({
        database: 'subscriptions-db',
        event: 'update-subscription',
        where: { id: subscriptionId },
        data: {
          last_payment_at: new Date().toISOString(),
          next_billing_date: new Date(
            Date.now() + 30 * 24 * 60 * 60 * 1000
          ).toISOString(),
          failed_payments: 0,
        },
      });
    });

    // Step 6: Generate invoice
    await ctx.step('generate-invoice', async () => {
      const invoice = await ctx.api.run({
        app: 'invoice-service',
        event: 'generate',
        input: {
          body: {
            subscriptionId,
            chargeId: paymentResult.id,
            amount,
          },
        },
      });

      return invoice;
    });

    // Step 7: Send receipt (non-critical)
    await ctx.step(
      'send-receipt',
      async () => {
        await ctx.notification.email({
          notification: 'billing',
          event: 'payment-receipt',
          recipients: [subscription.email],
          template: {
            amount,
            chargeId: paymentResult.id,
            date: new Date().toLocaleDateString(),
          },
        });
      },
      null,
      { allow_fail: true }
    );

    return {
      success: true,
      chargeId: paymentResult.id,
      amount,
      nextBillingDate: new Date(
        Date.now() + 30 * 24 * 60 * 60 * 1000
      ).toISOString(),
    };
  },
});

Approval Feature​

Multi-level approval process with escalation:

await ductape.features.define({
  tag: 'expense-approval',
  name: 'Expense Approval',

  signals: {
    'manager-decision': { input: { approved: 'boolean', comments: 'string' } },
    'director-decision': { input: { approved: 'boolean', comments: 'string' } },
    'finance-decision': { input: { approved: 'boolean', comments: 'string' } },
  },

  queries: {
    'getStatus': {
      handler: (ctx) => ({
        requestId: ctx.input.requestId,
        amount: ctx.input.amount,
        status: ctx.getState('status') || 'pending',
        currentApprover: ctx.getState('currentApprover'),
        approvals: ctx.getState('approvals') || [],
      }),
    },
  },

  handler: async (ctx) => {
    const { requestId, employeeId, amount, description } = ctx.input;

    ctx.setState('status', 'pending');
    ctx.setState('approvals', []);

    // Step 1: Create expense request
    const request = await ctx.step('create-request', async () => {
      return ctx.database.insert({
        database: 'expenses-db',
        event: 'create-request',
        data: {
          request_id: requestId,
          employee_id: employeeId,
          amount,
          description,
          status: 'pending_approval',
          created_at: new Date().toISOString(),
        },
      });
    });

    // Step 2: Get approval chain
    const approvalChain = await ctx.step('get-approval-chain', async () => {
      // Determine required approvers based on amount
      const chain = [];

      chain.push({ level: 'manager', required: true });

      if (amount > 1000) {
        chain.push({ level: 'director', required: true });
      }

      if (amount > 5000) {
        chain.push({ level: 'finance', required: true });
      }

      return chain;
    });

    ctx.setState('approvalChain', approvalChain);

    // Step 3: Manager approval
    ctx.setState('currentApprover', 'manager');

    await ctx.step('notify-manager', async () => {
      await ctx.notification.email({
        notification: 'approvals',
        event: 'approval-request',
        recipients: [ctx.input.managerEmail],
        template: {
          employeeName: ctx.input.employeeName,
          amount,
          description,
          approveUrl: `https://app.com/approve/${requestId}`,
        },
      });
    });

    const managerDecision = await ctx.waitForSignal('manager-decision', {
      timeout: '48h',
    });

    ctx.setState('approvals', [
      ...ctx.getState('approvals'),
      {
        level: 'manager',
        approved: managerDecision.approved,
        comments: managerDecision.comments,
        timestamp: Date.now(),
      },
    ]);

    if (!managerDecision.approved) {
      await ctx.step('mark-rejected', async () => {
        await ctx.database.update({
          database: 'expenses-db',
          event: 'update-request',
          where: { request_id: requestId },
          data: {
            status: 'rejected',
            rejected_by: 'manager',
            rejection_reason: managerDecision.comments,
          },
        });
      });

      await ctx.step('notify-rejection', async () => {
        await ctx.notification.email({
          notification: 'approvals',
          event: 'request-rejected',
          recipients: [ctx.input.employeeEmail],
          template: {
            amount,
            rejectedBy: 'Manager',
            reason: managerDecision.comments,
          },
        });
      });

      return {
        success: false,
        status: 'rejected',
        rejectedBy: 'manager',
        reason: managerDecision.comments,
      };
    }

    // Step 4: Director approval (if needed)
    if (amount > 1000) {
      ctx.setState('currentApprover', 'director');

      await ctx.step('notify-director', async () => {
        await ctx.notification.email({
          notification: 'approvals',
          event: 'approval-request',
          recipients: [ctx.input.directorEmail],
          template: {
            employeeName: ctx.input.employeeName,
            amount,
            description,
            managerApproved: true,
            approveUrl: `https://app.com/approve/${requestId}`,
          },
        });
      });

      const directorDecision = await ctx.waitForSignal('director-decision', {
        timeout: '48h',
      });

      ctx.setState('approvals', [
        ...ctx.getState('approvals'),
        {
          level: 'director',
          approved: directorDecision.approved,
          comments: directorDecision.comments,
          timestamp: Date.now(),
        },
      ]);

      if (!directorDecision.approved) {
        // Similar rejection handling...
        return { success: false, status: 'rejected', rejectedBy: 'director' };
      }
    }

    // Step 5: Finance approval (if needed)
    if (amount > 5000) {
      ctx.setState('currentApprover', 'finance');

      await ctx.step('notify-finance', async () => {
        await ctx.notification.email({
          notification: 'approvals',
          event: 'approval-request',
          recipients: [ctx.input.financeEmail],
          template: {
            employeeName: ctx.input.employeeName,
            amount,
            description,
            previousApprovals: ctx.getState('approvals'),
            approveUrl: `https://app.com/approve/${requestId}`,
          },
        });
      });

      const financeDecision = await ctx.waitForSignal('finance-decision', {
        timeout: '72h',
      });

      ctx.setState('approvals', [
        ...ctx.getState('approvals'),
        {
          level: 'finance',
          approved: financeDecision.approved,
          comments: financeDecision.comments,
          timestamp: Date.now(),
        },
      ]);

      if (!financeDecision.approved) {
        return { success: false, status: 'rejected', rejectedBy: 'finance' };
      }
    }

    // Step 6: Mark as approved
    ctx.setState('status', 'approved');

    await ctx.step('mark-approved', async () => {
      await ctx.database.update({
        database: 'expenses-db',
        event: 'update-request',
        where: { request_id: requestId },
        data: {
          status: 'approved',
          approved_at: new Date().toISOString(),
          approvals: ctx.getState('approvals'),
        },
      });
    });

    // Step 7: Initiate reimbursement
    await ctx.step('initiate-reimbursement', async () => {
      await ctx.messaging.produce({
        event: 'payroll-events:process-reimbursement',
        message: {
          requestId,
          employeeId,
          amount,
          approvals: ctx.getState('approvals'),
        },
      });
    });

    // Step 8: Notify employee
    await ctx.step('notify-approval', async () => {
      await ctx.notification.email({
        notification: 'approvals',
        event: 'request-approved',
        recipients: [ctx.input.employeeEmail],
        template: {
          amount,
          description,
          expectedPayment: 'Next payroll cycle',
        },
      });
    });

    return {
      success: true,
      status: 'approved',
      approvals: ctx.getState('approvals'),
    };
  },
});

Data Sync Feature​

Synchronize data between systems with conflict resolution:

await ductape.features.define({
  tag: 'data-sync',
  name: 'Data Synchronization',

  options: {
    timeout: 600000,
    rollback_strategy: 'to_checkpoint',
  },

  handler: async (ctx) => {
    const { sourceSystem, targetSystem, entityType, batchSize = 100 } = ctx.input;

    ctx.log.info('Starting data sync', { sourceSystem, targetSystem, entityType });

    // Step 1: Get last sync checkpoint
    const lastSync = await ctx.step('get-last-sync', async () => {
      const result = await ctx.database.query({
        database: 'sync-db',
        event: 'get-sync-state',
        params: { source: sourceSystem, target: targetSystem, entity: entityType },
      });
      return result[0] || { lastSyncedAt: null, lastSyncedId: null };
    });

    // Step 2: Fetch changed records from source
    const sourceRecords = await ctx.step('fetch-source-records', async () => {
      return ctx.api.run({
        app: sourceSystem,
        event: 'get-records',
        input: {
          body: {
            entityType,
            modifiedAfter: lastSync.lastSyncedAt,
            limit: batchSize,
          },
        },
      });
    });

    if (sourceRecords.records.length === 0) {
      ctx.log.info('No records to sync');
      return { success: true, synced: 0, conflicts: 0 };
    }

    ctx.setState('totalRecords', sourceRecords.records.length);
    ctx.setState('syncedRecords', 0);
    ctx.setState('conflicts', []);

    await ctx.checkpoint('records-fetched', {
      count: sourceRecords.records.length,
    });

    // Step 3: Process each record
    for (const record of sourceRecords.records) {
      await ctx.step(`sync-record-${record.id}`, async () => {
        // Check for existing record in target
        const existing = await ctx.api.run({
          app: targetSystem,
          event: 'get-record',
          input: { params: { id: record.id } },
        });

        if (existing && existing.modifiedAt > record.modifiedAt) {
          // Conflict: target is newer
          const conflicts = ctx.getState('conflicts') || [];
          conflicts.push({
            recordId: record.id,
            sourceModified: record.modifiedAt,
            targetModified: existing.modifiedAt,
          });
          ctx.setState('conflicts', conflicts);
          ctx.log.warn('Sync conflict detected', { recordId: record.id });
          return { skipped: true, reason: 'conflict' };
        }

        // Sync the record
        if (existing) {
          await ctx.api.run({
            app: targetSystem,
            event: 'update-record',
            input: { body: record },
          });
        } else {
          await ctx.api.run({
            app: targetSystem,
            event: 'create-record',
            input: { body: record },
          });
        }

        const synced = (ctx.getState('syncedRecords') || 0) + 1;
        ctx.setState('syncedRecords', synced);

        return { synced: true };
      });
    }

    // Step 4: Update sync state
    const lastRecord = sourceRecords.records[sourceRecords.records.length - 1];
    await ctx.step('update-sync-state', async () => {
      await ctx.database.update({
        database: 'sync-db',
        event: 'update-sync-state',
        where: { source: sourceSystem, target: targetSystem, entity: entityType },
        data: {
          lastSyncedAt: new Date().toISOString(),
          lastSyncedId: lastRecord.id,
          recordsSynced: ctx.getState('syncedRecords'),
          conflictsFound: ctx.getState('conflicts')?.length || 0,
        },
      });
    });

    // Step 5: Report conflicts if any
    const conflicts = ctx.getState('conflicts') || [];
    if (conflicts.length > 0) {
      await ctx.step(
        'report-conflicts',
        async () => {
          await ctx.notification.email({
            notification: 'system-alerts',
            event: 'sync-conflicts',
            recipients: [ctx.input.adminEmail],
            template: {
              sourceSystem,
              targetSystem,
              entityType,
              conflictCount: conflicts.length,
              conflicts,
            },
          });
        },
        null,
        { allow_fail: true }
      );
    }

    return {
      success: true,
      synced: ctx.getState('syncedRecords'),
      conflicts: conflicts.length,
      hasMore: sourceRecords.hasMore,
    };
  },
});

Tips for Building Features​

1. Design for Failure​

Always assume steps can fail. Define rollback handlers for critical operations:

await ctx.step('critical-op', doWork, undoWork, { critical: true });

2. Use Checkpoints for Long Features​

Break long features into phases:

await ctx.checkpoint('phase-1-complete');

3. Keep Steps Atomic​

Each step should do one thing well:

// Good: Single responsibility
await ctx.step('charge-card', chargeCard);
await ctx.step('send-receipt', sendReceipt);

// Bad: Multiple responsibilities
await ctx.step('process-payment', async () => {
  await chargeCard();
  await sendReceipt();
  await updateInventory();
});

4. Use allow_fail for Non-Critical Steps​

await ctx.step('analytics', trackEvent, null, { allow_fail: true });

5. Implement Idempotency​

Use idempotency keys for external operations:

await ctx.api.run({
  app: 'stripe',
  event: 'charge',
  input: {
    headers: { 'Idempotency-Key': `${ctx.feature_id}-payment` },
  },
});