unleash.unleash/website/docs/topics/feature-flags/limit-payloads.md

title
5. Limit payloads. Feature flag payload should be as small as possible.

Minimizing the size of feature flag payloads is a critical aspect of maintaining the efficiency and performance of a feature flag system. The configuration of your feature flags can vary in size depending on the complexity of your targeting rules. For instance, if you have a targeting engine that determines whether a feature flag should be active or inactive based on individual user IDs, you might be tempted to include all these user IDs within the configuration payload. While this approach may work fine for a small user base, it can become unwieldy when dealing with a large number of users.

If you find yourself facing this challenge, your instinct might be to store this extensive user information directly in the feature flagging system. However, this can also run into scaling problems. A more efficient approach is to categorize these users into logical groupings at a different layer and then use these group identifiers when you evaluate flags within your feature flagging system. For example, you can group users based on their subscription plan or geographical location. Find a suitable parameter for grouping users, and employ those group parameters as targeting rules in your feature flagging solution.

Imposing limitations on payloads is crucial for scaling a feature flag system:

1. Reduced Network Load:

   • Large payloads, especially for feature flag evaluations, can lead to increased network traffic between the application and the feature flagging service. This can overwhelm the network and cause bottlenecks, leading to slow response times and degraded system performance. Limiting payloads helps reduce the amount of data transferred over the network, alleviating this burden. Even small numbers become large when multiplied by millions.

2. Faster Evaluation:

   • Smaller payloads reduce latency which means quicker transmission and evaluation. Speed is essential when evaluating feature flags, especially for real-time decisions that impact user experiences. Limiting payloads ensures evaluations occur faster, allowing your application to respond promptly to feature flag changes.

3. Improved Memory Efficiency:

   • Feature flagging systems often store flag configurations in memory for quick access during runtime. Larger payloads consume more memory, potentially causing memory exhaustion and system crashes. By limiting payloads, you ensure that the system remains memory-efficient, reducing the risk of resource-related issues.

4. Scalability:

   • Scalability is a critical concern for modern applications, especially those experiencing rapid growth. Feature flagging solutions need to scale horizontally to accommodate increased workloads. Smaller payloads require fewer resources for processing, making it easier to scale your system horizontally.

5. Lower Infrastructure Costs:

   • When payloads are limited, the infrastructure required to support the feature flagging system can be smaller and less costly. This saves on infrastructure expenses and simplifies the management and maintenance of the system.

6. Reliability:

   • A feature flagging system that consistently delivers small, manageable payloads is more likely to be reliable. It reduces the risk of network failures, timeouts, and other issues when handling large data transfers. Reliability is paramount for mission-critical applications.

7. Ease of Monitoring and Debugging:

   • Smaller payloads are easier to monitor and debug. When issues arise, it's simpler to trace problems and identify their root causes when dealing with smaller, more manageable data sets.