Massive Email Delivery at Peak Scale

Massive Email Delivery at Peak Scale with Zero Failure

For a marketing platform serving thousands of hotels, peak-season reliability is non-negotiable. Under Black Friday traffic, the system’s behavior became unpredictable. So we re-engineered it to remain stable under extreme load.

The result is a workflow that remains stable even when every hotel sends millions of emails at once.

Overview

  • Client: Hospitality technology provider

  • Industry: Travel & Hospitality

  • Solution: High-performance audience segmentation engine and peak-load readiness enhancements

  • Outcome: 6 million emails sent per hour with minimal delays and zero peak-season incidents

Challenges

1

Platform Instability Under Peak Load

Traffic during Thanksgiving week routinely pushed the system beyond its limits, leading to delays and failed sends.

2

A Bottlenecked Segmentation Engine

The graph-based audience builder couldn’t return qualified profiles fast enough, slowing down time-sensitive campaign flows.

3

Campaigns With Zero Tolerance for Delay

Hotels rely on timely and reliable campaigns to drive direct revenue. Any slowdown or failure during this period has an immediate business impact.

What We Did

Engineering Approach

We had to transform a fragile, legacy-burdened segmentation pipeline into a resilient, observable system capable of sustaining extreme, time-compressed traffic without sacrificing accuracy. We treated architecture, data flows, and performance as a single problem space, using telemetry, rigorous load testing, and iterative validation to engineer reliability into every layer.

Rebuilt the Segmentation Engine for High Performance

We redesigned the audience selection engine using a streamlined Java/Spring Boot architecture. The old graph-based implementation couldn’t keep up with peak-season traffic, so we replaced it with a faster, more predictable API that could return large segments in seconds, even under extreme load.

Optimized and Modernized Data Infrastructure

We improved the performance of the existing Neo4j graph database layer and began the shift toward a new architecture using OpenSearch and ScyllaDB. This foundation removes scaling ceilings and prepares the platform for significantly higher throughput in upcoming peak seasons.

Validated System Behavior Through Production-Level Load Testing

Using Gatling and Python-based validation scripts, we simulated Black Friday traffic patterns end-to-end. These tests exposed latency spikes, throughput constraints, and hot paths that only appeared at scale, allowing us to resolve them before peak week.

Resilience Under Extreme Load

We tightened API communication paths, reduced latency variance, and eliminated slowdowns that previously cascaded into system-wide delays. The result was a stable, responsive platform during high-volume sends.

Strengthened Observability and Monitoring

We expanded Datadog monitoring across critical paths, giving real-time visibility into latency, query performance, and segmentation behavior. This telemetry allowed both engineering and marketing teams to detect and act on issues early, long before they became incidents

Validated Data Integrity at Scale

We built comparison scripts to validate that the new segmentation engine produced correct results at scale. This ensured that speed improvements did not come at the expense of targeting precision.

Established a Repeatable Black Friday Readiness Process

Through the cycle of testing, tuning, and verification, we created a structured approach to peak-season preparation, load-testing schedules, monitoring baselines, regression checks, and coordination patterns that can now be reused every year.

Integrated AI Features in the Email Editor

Outside of the Black Friday load-handling work, we implemented AI-powered content generation and auditing features in the platform’s email editor, helping marketers build and validate campaigns quickly and consistently.
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The Impact

Real-time Grid Monitoring

6 Million Emails Per Hour, Zero Incidents

The platform delivered its smoothest Black Friday and Cyber Monday to date, handling peak traffic for thousands of hotels with minimal delays and no outages.

Smooth communication between support tiers

Trust Restored Across Stakeholders

Hotels saw their campaigns sent on time. Internal teams saw stability where there had been uncertainty. Operational predictability improved.

Faster time-to-market

Faster, More Reliable Segmentation

The redesigned engine returned audiences more quickly and with higher accuracy, improving overall campaign quality.

BRAND ELEVATION

Ready to Scale Even Further

The new infrastructure is built to handle significantly higher throughput. Volume targets for the next cycle have doubled, and migrations are underway.

A successful new digital CX

A Proven Black Friday/Cyber Monday Readiness Playbook

Load-testing sequences, monitoring baselines, and validation workflows now form a repeatable process for every peak season.

Seamless augmented team

Better Cross-Team Coordination

Daily collaboration between API, data, and marketing teams improved communication, reduced bottlenecks, and sped up delivery.

An Organization-wide Impact

Year-Round Performance Gains

Improvements to the segmentation engine and API stack increased platform stability and responsiveness beyond peak periods.

OUR TECH PROFILE

Here’s a look at how we approach modernization and AI, the capabilities we bring to every project, and proof of impact through client success across industries.

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