What This Is
We connect your business systems to the Klaviyo API so customer profiles, behavioural events and engagement data move between your application and Klaviyo without anyone exporting a CSV. The work covers profile sync, custom event tracking, list management and pulling campaign results back out, all written as server-side code inside your application.
This is not a plugin install. Klaviyo’s built-in integrations cover the common shop platforms well, and if you run one of those you should start there. We build for the data those integrations never see: a subscription upgrade, a support ticket closed, a quote accepted, a usage milestone in your own software. Once those events reach Klaviyo, your marketing team can build segments and flows on what customers did, rather than on which list they happen to be on.
A SaaS platform is a good example. It sends signup, onboarding completed, feature used and plan changed as Klaviyo events. Marketing then builds a welcome sequence on signup, a nudge when onboarding stalls for three days, and a win-back flow when weekly usage drops to zero. None of that depends on Klaviyo’s JavaScript snippet loading in someone’s browser.
How a Klaviyo JSON Integration Works
Klaviyo’s current APIs follow the JSON:API specification. Every request and response is JSON with a fixed shape: a data object carrying a type (such as profile or event), an attributes object holding the fields, and a relationships object linking records together, so an event points at the profile and the metric it belongs to. Each call also sends a revision header, a date that pins the version of the API your code was written against.
Two practical consequences matter when you are paying for an integration.
First, the payload has to be built properly. A purchase event is a JSON body naming the metric (“Placed Order”, say), the profile it belongs to by email or external ID, a value, and a properties object with the line items, order number and anything else you want to segment on later. Get the property names wrong or change them between releases and your segments stop matching without any error, so we agree the names up front and treat them as a contract.
Second, revisions expire. Klaviyo supports each dated revision for two years, one stable and one deprecated, before retiring it. The older v1 and v2 endpoints such as Track and Identify have been replaced by the Events and Profiles APIs. If your current integration still calls those, or was written against a revision from a few years ago, it needs updating before it stops working. We pin the revision in one place in the code and note when it is due for review.
Klaviyo Profile Enrichment
Profile enrichment means writing data from your own systems onto the Klaviyo profile as custom properties: plan tier, account owner, lifetime value, last support contact, renewal date, the branch a customer uses. Klaviyo segments can then filter on those properties directly.
The data usually lives in places Klaviyo cannot reach: your application database, a CRM, a billing system, a booking tool. We sync it on a schedule or whenever it changes, matching profiles on email or your own customer ID so one person doesn’t become three Klaviyo profiles. If you want to bring in third-party data as well, such as company size from an enrichment provider, the same job looks it up and writes the result to the profile, with the source recorded next to it.
A specific case: a B2B software firm wants renewal emails to go only to account admins whose contract ends in 60 days and who have logged in this month. Klaviyo cannot know any of that on its own. A nightly job writes role, renewal_date and last_login to each profile,, and the segment filters on those three fields.
When You Need This
Klaviyo API integration is the right choice when you need server-side event tracking and profile management beyond what Klaviyo’s built-in integrations provide. The usual triggers:
- Application-specific events such as subscription changes, feature usage or milestones that no native integration captures
- Backend data on the profile: subscription tier, lifetime value, support history or usage metrics
- Email and SMS driven from the same events, so a customer gets one message on the right channel rather than two
- Engagement data coming back the other way, with campaign opens, clicks and flow activity written into your user records or CRM
- A legacy integration on the old Track and Identify endpoints that needs moving to the current APIs
If your shop runs on WooCommerce, the WooCommerce and Klaviyo integration covers that pairing specifically, and WhatsApp and Klaviyo covers adding WhatsApp to your flows.
How We Work
Every Klaviyo build starts with an event catalogue and a profile schema: which actions become events, which properties each event carries, which fields sync to the profile, and which system owns each one. Your marketing team signs that off before we write code, because it is what their flows and segments will be built against.
We authenticate with a private API key scoped to the access the integration needs. Events go through the Events API with full property payloads, profile changes through the Profiles API, and every call is dispatched through a queue so tracking never slows down your application. Klaviyo applies rate limits per endpoint, so the queue spaces requests out and retries a failed call rather than dropping it. Each request and response is logged, which means a missing event can be found and replayed.
List and segment work is handled through the API where it has to be programmatic: adding subscribers at checkout, removing profiles when an account is deleted, or keeping list membership in step with account status. Klaviyo webhooks feed flow and campaign engagement back into your application where you need it.
What You Get
- Server-side event tracking with rich property payloads, independent of frontend JavaScript
- Profile enrichment from your own systems for segmentation, matched on a stable customer ID
- List and segment sync driven by application events
- Events used across email and SMS flows from a single integration
- Campaign and flow results pulled back into your application for reporting
- Consent and opt-in status kept in step between your application and Klaviyo
- A written event catalogue and a pinned API revision, so the next developer knows what is sent and why
Technologies We Use
- Klaviyo API: Events, Profiles, Lists, Segments, Campaigns and Metrics endpoints, JSON:API format with a pinned revision header
- Laravel: queued event dispatch, profile sync jobs and webhook handling
- PostgreSQL: event logs, profile ID mapping and engagement data
- Redis: rate limiting and batched queues
Related Systems
A Klaviyo integration links your marketing automation to the systems that hold the real customer record: an e-commerce backend tracking purchases, a subscription product triggering lifecycle emails from usage, or a CRM enriched with marketing engagement. Where the aim is a wider operational workflow rather than marketing, see business automation. For list-based email marketing rather than behavioural automation, see Mailchimp API integration. Both sit within our broader API integration services.
Talk to Us About Your Klaviyo Integration
If you want events from your own systems driving your email and SMS, or an older Klaviyo integration moved onto the current API before its revision retires, get in touch and we will start with the event catalogue.
