Sends tracking requests
Backend & Runtime / Knowledge library
Load Balancing
Distributes requests across available service instances
Why learn Load Balancing?
It scales throughput and routes around unhealthy nodes
The problem it solves
It prevents one server from becoming the only capacity or failure point
Where it came from
Load Balancing is a networking and web concept that distributes requests across available service instances. Its guarantees and tradeoffs depend on the concrete implementation and operating context.
Build your understanding
Work through these exercises in order. Try the task before opening a reference.
- Define Load Balancing and distinguish it from a neighboring concept.
- Choose a realistic task where Load Balancing is appropriate.
- Identify a failure mode caused by misusing Load Balancing.
- Interpret a small design or result involving Load Balancing.
- Explain one tradeoff or limitation of Load Balancing.
Documentation and sources
- MDN Web Technology Glossary (developer.mozilla.org)
Connect the ideas
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Real World Example
Optimizing Regional Logistics Portal Traffic
A regional logistics firm managing a high-volume portal for real-time delivery tracking and driver dispatching.
The business problem
The firm experiences service outages during peak morning dispatch hours because a single monolithic server instance cannot handle the concurrent connection spikes from thousands of mobile driver devices, leading to request timeouts and dispatch delays.
How this topic solves it
By deploying a load balancer, the firm distributes incoming traffic across a cluster of identical service instances. This ensures that no single server becomes a bottleneck, as the load balancer acts as a reverse proxy that intelligently routes requests to the least busy instance, maintaining system availability even when individual nodes are under heavy load.
- Provision multiple identical service instances to host the logistics application logic.
- Configure the load balancer to perform health checks on each service instance to verify responsiveness.
- Update the DNS records to point the logistics portal domain to the load balancer's public IP address.
- Define a distribution algorithm, such as round-robin, to cycle incoming requests through the healthy instance pool.
This diagram illustrates how client requests are intercepted by the load balancer and distributed to backend servers.
Distributes incoming traffic
Processes request
Processes request
- Driver Device → HTTP Request → Load Balancer
- Load Balancer → Route to Instance A → Instance A
- Load Balancer → Route to Instance B → Instance B
Expected business outcome
The logistics portal achieves improved reliability and consistent response times for drivers, as the system gracefully handles traffic spikes by spreading the workload across the available infrastructure.
Limitations and checks
A primary limitation is the potential for session persistence issues; if a user's state is stored locally on one server, they may lose their session if the load balancer routes them to a different instance. To check for this, monitor application logs for frequent authentication errors or session-related exceptions during peak traffic periods.