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Case File · INV-0051

Pricing page froze 25 minutes after a CMS update

A missing tag mapping and a silent TypeError combined to block every revalidation job — leaving SimUser AI's pricing page stuck on old data right before a 15% price repositioning went live.

5 min readHighStale pricing visible to leadsFixed by CauseFlow in 3 min

The Symptom

On April 16, 2026, Felipe Aguiar (Head of Marketing, SimUser AI) pushed a 15% price update across all plans via Contentful at 11:20 UTC. At 11:45 UTC a lead confirmed the /pricing page still showed the old numbers. The marketing team had already shared the updated pricing in an email blast — visitors clicking through saw stale data.

11:20 UTC — CMS publish11:45 UTC — first report

Evidence Board

DynamoDB · Revalidation Job
tag:          "revalidate"
path:         "/pricing"
status:       "pending"
retries:      3
error:        "TypeError: Cannot read properties
               of undefined (reading NewImage)
               at handler (/var/task/index.js:23:45)"
deployId:     "deploy-20260416-030158"
deployVersion:"v2.4.0"
timestamp:    "2026-04-16T03:02:14Z"
DynamoDB · Cache Entries (71 rows)
71 rows returned — all paths containing "/pricing"
tag:          "{deployId}/_N_T_/[locale]/pricing/page"
path:         "{deployId}/en/pricing"
revalidatedAt:"1"   ← never revalidated since deploy
→ No cache invalidation reached any /pricing variant.
CloudWatch · Seeder Lambda
Log group: /aws/lambda/simuser-ai-production-
           WebsiteRevalidationSeederFunction
{"level":"warn",
 "msg":"Tag not found in revalidation table",
 "tag":"pricing-page",
 "pathCount":0,
 "note":"No paths registered for this tag — skipping"}
Affected Routes
  • /
  • /pricing
  • /features
  • /blog/simuser-ai-v2-launch
  • /blog/…

Where the Pipeline Broke

Two overlapping bugs blocked every revalidation attempt. Hover each X to see the failing code.

CMSContentfulWebhookHTTP POSTSeederLambdaDynamoDBTableSubscriberLambdaNext.jsBug 1: Missing tag mapping"pricing-page" → no paths registeredSeeder skips — pathCount: 0Bug 2: TypeError at handler:23record.dynamodb.NewImage undefinedon DELETE events → retries: 3 → stuckworking pathblocked path✕failure point (hover for details)

Systemic Blast Radius

The TypeError in the Subscriber handler affected every route that had a queued revalidation job — not just /pricing. Any page touched by a DynamoDB Streams event during this window was silently stuck.

  • /
  • /pricing
  • /features
  • /blog/simuser-ai-v2-launch
  • /blog/…

Symptom → Root Cause

  1. 1

    Symptom: /pricing shows stale prices

    ↳ Lead reports old plan prices; CMS publish was 25 min ago.

  2. 2

    DynamoDB job stuck at retries: 3

    ↳ TypeError on NewImage blocks all revalidation jobs — any DELETE event crashes the handler.

  3. 3

    Seeder skips /pricing entirely

    ↳ Tag 'pricing-page' has no paths registered in the revalidation table; pathCount: 0.

  4. 4

    Root cause: two overlapping bugs

    ↳ Missing tag map + unguarded NewImage access = no revalidation ever reaches Next.js.

Root Cause & Fix

Bug 1 — Missing tag mapping

The CMS webhook sends the tag pricing-page, but no entry in the DynamoDB table maps that tag to the /pricing path. The Seeder logs a warn and exits without queuing any invalidation.

Bug 2 — Unguarded NewImage access

The RevalidationEventsSubscriber reads event.Records[i].dynamodb.NewImage unconditionally. DynamoDB Streams DELETE events omit NewImage, causing a TypeError that puts every affected job into an unrecoverable retries: 3 / status: pending state.

Before — handler crashes on DELETE eventsjavascript
// handler (/var/task/index.js:23)
const newImage = record.dynamodb.NewImage; // crashes on DELETE events
await revalidatePath(newImage.path.S);
After — guarded handlerjavascript
// handler (/var/task/index.js:23)
const newImage = record.dynamodb?.NewImage;
if (!newImage) return; // guard: DELETE

await revalidatePath(newImage.path.S);

Additionally: register the tag pricing-page → /pricing in the revalidation table and audit all other CMS tags to ensure they map to the correct Next.js paths.

Outcome

Without CauseFlow: ~3 hrs of cross-team debugging across CloudWatch, DynamoDB console, and Lambda logs — with the reputational cost of stale pricing visible to inbound leads during a live price repositioning.

With CauseFlow: root cause surfaced in 25 minutes, fix committed before any further leads landed on the page.

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