Call Loop – Custom Voice & SMS Marketing Software

About the client

Call Loop is a multi-channel text marketing software designed to automate customer outreach, allowing organizations to run targeted campaigns using SMS messaging, ringless voicemails, and voice broadcasts.

Country:

USA

Industry:

Marketing

Service:

Marketing software development

Duration

March, 2022 – ongoing

Model:

B2B, SaaS

Team size:

1 project manager, 1 front-end developer, 2 back-end developers, 1 DevOps, 2 QA engineers, 1 designer

Key technologies:

React, Java, AWS Services

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Client’s challenge

As the client’s text marketing app grew, its original version, Call Loop 1.0, reached a technological limit. The outdated technology, the extensive use of custom-written code, and the backend's dispersed nature led to unstable platform performance and time-consuming maintenance.

Outdated design
Fragmented backend architecture
Inefficient custom-written code
Unstable performance and recurring bugs
Time-consuming maintenance

Solution

Our team took the original Call Loop 1.0 product and rebuilt it into a faster and much simpler tool to use. Alongside a clutter-free UX/UI design and a modern tech foundation, we added tools that the old system couldn't support, such as multi-channel messaging and detailed delivery analytics.

New service-oriented architecture

We broke apart the legacy monolith and moved Call Loop 1.0 to a modular cloud architecture on AWS. The new system separates operations across three services: a Config Service for business logic and integrations, a Billing Service for payments, and a serverless Lambda Layer for message delivery. Connected through HTTP and asynchronous AWS SQS queues, this architecture isolates heavy campaign traffic and makes the platform easier to scale and maintain.

New custom functionality

NEKLO transformed Call Loop 1.0 into a unified platform for bulk SMS campaigns, voice broadcasts, and ringless voicemail drops. We added smart autoresponders, direct CRM integrations, and real-time delivery analytics within a single system. Users can now manage multiple communication channels from one place while tracking campaign performance and conversion metrics as results come in.

Enhanced usability

We redesigned Call Loop 2.0 with a cleaner UI/UX and simpler navigation across core workflows. To address the 2–5 business days required for mobile carriers to verify real numbers, we also streamlined onboarding. Users complete a short compliance form that is automatically submitted to carriers and receive a temporary test number, allowing them to start testing SMS campaigns immediately.

Phased data migration

Our team migrated user profiles, contacts, and account history from Call Loop 1.0 to the new platform in phases. The migration approach kept existing data intact while allowing customers to continue using the service throughout the transition. This enabled Call Loop to move its user base to version 2.0 without disrupting day-to-day operations.

Process

To modernize Call Loop 1.0 without interrupting daily business for active users, NEKLO took a phased approach. Our team built the new platform alongside the old one and moved users over gradually.

1. Legacy platform audit

We began with a detailed audit of Call Loop 1.0, mapping its hidden dependencies, database bottlenecks, and fragile scripts. This gave us the exact blueprint needed to design a service-oriented architecture for Call Loop 2.0.

2. Platform rebuild & data migration

Next, our team rebuilt the core messaging engine. We moved the platform onto scalable AWS infrastructure and introduced asynchronous message queues. With the new architecture ready, we handled data migration through a staged rollout, so Call Loop stayed fully operational with no disruptions to end users.

3. Performance optimization

Finally, we implemented end-to-end monitoring and observability so the development team could track system health and resolve latency spikes before users ever noticed them.

1. Legacy platform audit

2. Platform rebuild & data migration

3. Performance optimization

Finally, we implemented end-to-end monitoring and observability so the development team could track system health and resolve latency spikes before users ever noticed them.

Technologies

Front-end

GraphQL

React

REST API

TypeScript

Back-end

Apache Kafka

GraphQL

Java

Java Persistence API

Node.js

RabbitMQ

REST API

Spring Boot

TypeScript

DevOps

AWS Amazon OpenSearch Service

AWS API Gateway

AWS Aurora

AWS CloudFront

AWS CloudWatch

AWS EC2

AWS ECR

AWS EKS

AWS ElastiCache

AWS Lambda

AWS MSK

AWS S3

AWS SQS

ELK Elasticsearch

ELK Integrations

ELK Kibana

Gradle

PostgreSQL

Prometheus

Redis

Deliverables

New app architecture

Implementation of the HTTP

Asynchronous queues

Proxy development

Automatic number verification

SMS marketing special features

Results

NEKLO upgraded Call Loop to a reliable platform, eliminating the dashboard freezes and delays caused by large messaging campaigns. NEKLO upgraded Call Loop to a faster, more reliable platform, fixing the constant slowdowns and crashes that frustrated users. At the same time, our engineers lowered the company’s monthly tech costs by moving away from expensive paid software like New Relic to efficient AWS tools.

At this moment Call Loop offers SMS marketing services in the US and Canada, with plans to expand to Europe and Australia. Our team ensures all data protection and storage practices strictly comply with the specific legal frameworks of each targeted region.

1,000

organizations served in the US and Canada

500

messages sent daily

4.5

Capterra rating