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Business productivity

Klaviyo to Resend integration — real-time, two-way sync

Keep Klaviyo and Resend in sync without custom scripts. Cut weeks of integration work, eliminate silent data drift, and give your team a single, reliable source of truth.

  • SOC 2 and 6 other compliance frameworks
  • POC with real engineers in minutes

Adopted by fast-scaling companies moving mission-critical data in real time

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Why teams connect Klaviyo and Resend

Stop re-entering the same information in Klaviyo and Resend: Stacksync keeps the records they share consistent in real time, in both directions.

Two tools in the daily stack often hold overlapping information: the same people, the same companies, or the same pieces of work, described twice. The tools do different jobs, so consolidating is not the answer; the overlap just needs to stop drifting.

Stacksync syncs Catalog Items, Tags, Profiles, Lists in Klaviyo with Emails, Contacts, Audiences, Broadcasts in Resend in real time. You choose which records overlap, map the fields that should match, and pick a direction or let changes flow both ways. From then on, an update made in either tool is reflected in the other within seconds, without exports or copy-paste.

Because the sync is field-level, each tool keeps its own extras; only the shared data is held in agreement.

Common use cases

  • Sync catalog items from an ERP or PIM so product recommendations and back-in-stock flows use current data
  • Sync customer profiles between Klaviyo and the CRM or warehouse so segments can use fields beyond storefront data
  • Feed open and click events into a warehouse for engagement analytics alongside product data.
  • Sync CRM contact segments into Resend Audiences so lifecycle broadcasts target current data.

Where one tool produces events: mirror them in the other

Payments, replies, messages, or tickets created in one tool can create or update matching records in the other, keeping context in one place.

Where Resend is where the team documents or plans: keep its data fed

Information that originates in Klaviyo stays current in Resend instead of going stale after a one-time paste.

Handoffs between teams

When work started in one tool continues in the other, the shared fields travel with it automatically.

What you can sync between Klaviyo and Resend

Representative objects on each side — any object or custom field can map to any target. Schemas are auto-detected; types are converted between the two systems.

Klaviyo objects Resend objects
Profiles Person records with arbitrary custom properties are the target for CRM and warehouse-sourced attributes. Email events Delivered, bounced, complained, opened, and clicked events emitted via webhooks and written back to source systems.
Lists Static audience memberships sync in from CRMs and forms for targeting. API keys Scoped credentials managed per environment for send and read access.
Segments Dynamic audiences are readable so other tools can mirror who qualifies. Emails Sent messages retrievable by ID with current delivery status.
Events Timestamped behavioral records tied to metrics; external order and product events are pushed in to trigger flows. Contacts Recipient records with email, name, and subscription state, synced from CRMs or databases.
Metrics Event type definitions organize the activity stream used in segmentation and attribution. Audiences Named contact lists that broadcasts target; typically mirrored from CRM segments.
Campaigns Email and SMS sends expose performance data for warehouse-based reporting. Broadcasts One-to-many campaign sends addressed to an audience.
What ships with Klaviyo ⇄ Resend

Connect Klaviyo and Resend for flexible, real-time data sync.

Real-time sync, workflow automation, event queues, EDI, and monitoring, for every Klaviyo–Resend connection.

Real-time

Two-way sync

Changes in Klaviyo or Resend instantly reflect in both systems. No stale data, no manual imports.

No-code + pro-code

Workflow automation

Trigger automated workflows whenever Klaviyo or Resend data changes, update records, fire webhooks, or kick off sequences without brittle API scripts.

At scale

Event queues

Handle millions of events per minute without losing a single Klaviyo or Resend record.

Observability

Monitoring

Track your Klaviyo ⇄ Resend sync health, view errors, and replay failed events in one click.

Trading partners

EDI

Transform legacy EDI complexity into simple database interactions between Klaviyo and Resend.

How the Klaviyo and Resend connectors work

Klaviyo

Integration surface
REST API compliant with the JSON:API specification
Authentication
OAuth 2.0 for apps or private API keys
Change detection
Polling on updated timestamps; outbound webhooks exist for event topics (availability depends on plan or app-partner status) and as flow webhook actions
Capabilities
read · write · webhooks
Rate limits
Per-endpoint burst and steady rate limits apply

Resend

Integration surface
REST API
Authentication
API key (Bearer token)
Change detection
Webhooks for email lifecycle events; polling for contact and audience state
Capabilities
read · write · webhooks
How it works

How to connect Klaviyo to Resend — three steps, no code

Configure and sync within minutes, no code. Whether you sync 50k or 100M+ records, Stacksync handles the queues, infra, and plumbing. Integrations are non-invasive and need zero setup on your systems.

  1. 01

    Connect your apps

    Authenticate Klaviyo and Resend with each platform's native method — OAuth, API keys, or service accounts — plus secure options like SSH tunneling, IP whitelisting, and VPC peering.

    • OAuth 2.0
    • SSH tunnel
    • VPC peering
    Klaviyo connected
    Resend connected
    OAuth 2.0
    SSH tunnel
    SSL certificate
    VPC peering
  2. 02

    Choose tables

    Pick the Klaviyo and Resend objects to sync — Stacksync auto-detects both schemas, including custom fields where the platform exposes them. Sync to existing tables, or let Stacksync create new ones with ideal data types.

    • Standard objects
    • Custom objects
    • Auto-schema
    objects · Klaviyo ⇄ Resend
    Customers 12,480
    Sales Orders 8,213
    Invoices 5,902
    Items 1,344
  3. 03

    Map fields

    Fields map automatically even when names and types differ. Stacksync handles transformation and type casting for you, zero configuration required.

    • Auto-map
    • Type casting
    • Transforms
    Klaviyo Resend
    Company company_name text
    Email email text
    Amount amount numeric
    Created created_at timestamp
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FAQ

Klaviyo and Resend integration FAQ

SECURITY

Security teams love Stacksync

As a data company, we understand the importance of keeping your data secure. Stacksync is built with security best practices to keep your data safe at every layer, and is DPF-certified for US, EU, UK and CH data transfers.

Learn more about security
SOC 2 type II
ISO 27001
HIPAA BAA
GDPR
CCPA
CSA STAR
DPF US-EU-UK-CH
→ SECURITY WITH BENEFITS

SSO & SCIM

Let your users access Stacksync from your centralized user management systems. Works with Okta, Azure, Google SSO and more.

Alerts

Immediately get alerted about record syncing issues over email, Slack, PagerDuty and WhatsApp. Resolve issues from a centralized dashboard with retry and revert options.

Secure connection options

Securely connects to your systems with:

OAuth 2 SSH Tunnelling SSL certificates IP Whitelisting VPN gateway VPC peering and more

Related integrations

Every pair below is a real-time, two-way sync. Search all 386 integrations available for Klaviyo and Resend.

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