To keep your system running smoothly when millions of users access it at the same time, a Software Architect needs to consider many factors.
Below is a comprehensive checklist of bottlenecks and optimization solutions to ensure your system is always ready for high traffic.
1. Bottleneck from monolith architecture
All logic and resources are bundled together → difficult to scale
Solutions:
- Switch to microservices
- Make services stateless to allow horizontal scaling
- Add an API Gateway (rate-limiting, circuit breaker)
- Use a service mesh (Istio, Linkerd) if observability is needed
2. DB bottleneck due to too many direct queries
1 million users can generate tens of millions of DB queries
Solutions:
- Use a connection pool (HikariCP, PgBouncer)
- Read/Write splitting (Master-Slave)
- Caching layer (Redis/Memcached) for hot data
- Shard or partition large tables
3. Heavy tasks included in the main request flow
Sending emails, logging, image processing, etc. in the sync flow slows things down
Solutions:
- Use a message queue (Kafka, RabbitMQ, Redis Streams)
- Producers push jobs, consumers process asynchronously
- Retry logic with delay and dead-letter queues
4. Missing or poorly implemented caching
Querying data on every page load overwhelms the system
Solutions:
- Multi-layer cache: CDN → Redis → Local Cache
- Use correct TTL and cache invalidation
- Dynamic cache keys: user:{id}, homepage:{lang}
- Use cache-aside instead of write-through for frequently changing data
5. Unoptimized Frontend and APIs
The frontend spams too many APIs, large payloads, and lacks lazy loading
Solutions:
- Use GraphQL or Backend-for-Frontend (BFF) to consolidate APIs
- Enable GZIP, HTTP/2, and use CDN for static assets
- Debounce input and paginate all lists
- Use smart prefetching instead of loading everything at once
6. Infrastructure doesn’t auto-scale
Traffic spikes, but the app doesn’t scale accordingly
Solutions:
- Deploy on Kubernetes (HPA, VPA)
- Use autoscaling services like EC2, Cloud Run, Fargate
- Layer 7 Load Balancer (to block DDoS, smart traffic routing)