CosmosLevel
CosmosLevel is a multilingual SaaS (Software as a Service) platform designed to cater to professionals who operate on an appointment basis. The two main types of users are professionals who offer appointments and clients who book those appointments. Although primarily aimed at professionals, they too can book appointments with other professionals within the app, essentially making them clients as well.
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Key Outcome
Used by professionals across multiple countries
Technologies Used
Frontend
Backend
Database
Monitoring & Observability
Deployment & Infrastructure
Microservices & Integrations
Testing & QA
Packages
The Challenge
Professionals needed an all-in-one platform for appointment management, calendar synchronization, video conferencing, and payments — with multilingual support for a global user base.
Our Solution
We built a horizontally scalable SaaS platform with deep integrations into Zoom, Google Calendar, Stripe, and more. BullMQ handled distributed job scheduling, while Redis sentinels and MySQL InnoDB clusters ensured high availability.
Key Features
Benefits
💛 What We Love About This Project
The multilingual architecture that truly works for a global audience — every offer, profile, and notification adapts seamlessly.
How BullMQ distributes jobs elegantly across horizontal instances, making scaling feel effortless.
The deep Zoom and Google Calendar integrations that make scheduling feel native, not bolted on.
OpenReplay session replays gave us crystal-clear insight into user behavior — like sitting next to every user.
Infrastructure resilience — the platform survived cloud provider outages without any downtime thanks to MySQL InnoDB clusters and Redis sentinels.
The review system that builds genuine trust between professionals and clients.
🤝 What We Appreciate About Our Client
Their clear vision for what professionals truly need — they understood the pain points from day one.
The trust they placed in us to architect a complex, multi-service infrastructure from scratch.
Always available for feedback loops — quick decisions meant fast iteration cycles.
Their commitment to quality over shortcuts — they never pushed us to cut corners.
Open to innovative solutions like OpenReplay and feature flags that improved the product beyond the original scope.
Challenges We Faced
Connecting the infrastructure across multiple cloud providers
We run scheduled jobs horizontally on all or specific instances of the backend. We used BullMQ for NestJS — regardless of how many instances of the backend there are, the specific instances that we wanted to run specific jobs were picked up in a distributed balanced way. This not only improved the performance by being able to scale horizontally but also brought advanced job scheduling, repeatable jobs, and improved concurrency control.
Monitoring performance
We learned how to monitor and detect issues before they became serious. This included monitoring the uptime of the infrastructure, the steal and load time of each virtual machine, the status of Redis and MySQL InnoDB servers, the application queues status and errors, the status of cron jobs, and the backend and frontend errors and logs.
Cloud provider outages
We learned how to deal with outages and still keep the app running. The solution included MySQL InnoDB cluster, Redis sentinels, NATS, Nginx Reverse proxy balancing multiple backend services, and WebSockets that keep the connections in Redis so it can be scaled on multiple backend services.
User session replays for continuous improvement
OpenReplay saved us and brought a world full of clarity where we could actually replay the whole user session as if we were there with the user. This was immensely helpful for understanding user behavior and pinpointing issues.
Feature Flags
We integrated feature flags with OpenReplay, enabling us to quickly enable or disable features without deploying new code. This integration allows for streamlined experimentation and rapid iteration.
Funnels
Making sure that the user experience is aligned with how the app is designed is essential. We monitor and see various funnels that the user is going through to optimize the experience.
Multilingual Support
Implementing a system for managing multiple languages across the app interface, offers, and communication, ensuring accurate translations and localization.
Real-time Synchronization
Keeping calendars, availability, and appointment data synchronized across multiple users and devices in real-time. This requires robust backend infrastructure and careful handling of data updates.
Integration with Third-Party Services
Seamlessly integrating with external services like Google Meet, Zoom, and payment gateways while maintaining data security and user privacy. This involves API management, authentication protocols, and error handling.
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