We Found a Client Losing Half Their Leads to a Broken Form Sync

A head of marketing noticed it during a monthly review. Their landing page form showed [N] submissions last month. Their CRM (HubSpot) showed [N] new leads. The difference wasn't small — it was [PCT]%.

Where were the missing leads going?

Following the Data

Step 1: Is the form working?

Form renders: yes. Validation works: yes. Submit button clickable: yes. Success message shows: yes. But when we looked at the network tab during submission, we saw:

POST /api/leads

Status: 200 OK

Response: {"status": "success", "lead_id": "12345"}

The form was submitting successfully. The API was responding 200. So where were the leads?

Step 2: Is the API working?

API logs showed POST /api/leads 200 for every submission. The API was receiving requests and returning 200. But the CRM wasn't getting the leads.

Step 3: The integration gap

We traced the data flow. The API was writing to an internal database. There was a "nightly sync" job that was supposed to push leads to HubSpot. We checked the sync job:

def sync_leads_to_hubspot():

    leads = db.query("SELECT * FROM leads WHERE synced_at IS NULL")

    

    for lead in leads:

        try:

            hubspot.create_contact({

                'email': lead.email,

                'firstname': lead.first_name,

                'lastname': lead.last_name,

                'company': lead.company

            })

            lead.synced_at = datetime.now()

            db.commit()

        except Exception as e:

            logger.error(f"Failed to sync lead {lead.id}: {e}")

            # BUT: synced_at is NOT updated, so it will retry tomorrow

The sync job was failing silently. When HubSpot returned an error (duplicate email, invalid format, rate limit), the job logged the error but didn't mark the lead as "failed." It would retry the same lead every night, failing every time, and never processing the leads behind it.

The error log showed the same lead failing for [N] days straight. That lead (a duplicate email) was blocking [N] other leads from syncing. The queue was growing by [N] leads/day.

What We Found

We found [N] issues:

1. Silent failures: the sync job logged errors but didn't alert anyone. The error log was a file that nobody read.
2. No dead letter queue: failed leads stayed in the "unsynced" queue forever, blocking valid leads.
3. No validation: the API accepted any email format, including "test@test" and "user@domain" (missing TLD). HubSpot rejected these.
4. No real-time sync: leads were synced nightly. A lead who submitted at 9 AM wouldn't be in HubSpot until the next day. By then, the sales team had already called them from a manual export.
5. Duplicate handling: the API didn't check for existing leads. HubSpot rejected duplicates. The sync job didn't handle this gracefully.

What We Built

We redesigned the architecture: real-time validation, deduplication, HubSpot creation, then confirmation to the user. No more nightly sync. No more internal database as primary. HubSpot is the single source of truth.

Real-time validation: We validate email format, required fields, and check HubSpot for existing contacts before creating. If the contact exists, we update it instead of creating a duplicate. If the email is invalid, we reject it at the API level with a 400 response.

Client-side tracking: We added form tracking to capture events even if the API fails. Track form submit attempt, form success (on API 200), and form error (on API 4xx/5xx).

Monitoring and alerting: Real-time dashboard showing form submits → API responses → HubSpot creates (should be 1:1:1). Alert if API 200s ≠ HubSpot creates for >[N] minutes. Alert if API error rate >[PCT]%. Daily report: form submits, API successes, HubSpot creates, discrepancies.

The Results

The [PCT]% increase in leads wasn't more traffic — it was capturing the leads that were already submitting but getting lost. On a [SPEND] monthly ad spend, the recovered leads were worth approximately $[REVENUE] in pipeline.

What We Learned

The form is not the funnel. The form submit is step 1. The CRM entry is step 2. The sales follow-up is step 3. If step 2 breaks, step 3 never happens. We now map the entire lead flow, not just the form.

Silent failures are the worst failures. The sync job was "working" — it ran every night, logged errors, and continued. But it was failing at its actual job. We now require alerts on any integration job.

Real-time > batch. The nightly sync was a [N]-year-old decision when lead volume was low. At their current scale, real-time is necessary. Sales calls leads within [N] minutes of form submit. A [N]-hour delay means the lead is cold.

Validate at the edge. Email validation in the browser catches [PCT]% of invalid emails before they hit the API. API validation catches the rest. HubSpot never sees invalid data.

Deduplicate upstream. Checking HubSpot before creating prevents duplicates at the source. The old flow created duplicates in the internal DB, then failed at HubSpot. The new flow checks HubSpot first.

Bottom Line

This client was losing [PCT]% of their leads to a broken sync job. The fix wasn't a new form or a new CRM — it was real-time validation, deduplication, and monitoring. The implementation took [HOURS] hours and recovered $[REVENUE] in pipeline.

If your form submissions don't match your CRM, you have this problem. The question is how long you've had it.