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Keep-Alive Connections And Its Critical Role While Optimizing API Performance

by Albert Garcia

Nov 12, 2023

3 min read
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An important yet often overlooked aspect while optimizing API performance is the management of HTTP keep-alive connections. KrakenD, an advanced API Gateway, offers an array of configuration parameters that significantly influence these connections. This post delves into these parameters, elucidating how they affect API performance.

Understanding Keep-Alive in HTTP

HTTP keep-alive is a protocol mechanism that maintains an open connection between the client and the server. It allows multiple requests and responses over a single connection, reducing the overhead of establishing new connections, thus enhancing API performance. KrakenD’s transport layer, supporting HTTP and HTTPS, leverages this by caching connections for future use.

Key Keep-Alive Parameters in KrakenD

  1. dialer_keep_alive: This parameter defines the interval for keep-alive probes on an active network connection. Its default setting is "15s" (15 seconds), which helps in maintaining connection readiness without excessive network burden.
  2. disable_keep_alives: Contrary to keeping connections alive, this setting, when set to true, disables HTTP keep-alives, using the connection for only a single HTTP request. This can be useful in scenarios with short-lived or infrequent requests.
  3. max_idle_connections_per_host: Set by default to 250, this parameter limits the number of idle keep-alive connections per host. It strikes a balance between the benefits of keep-alive and potential resource overhead.
  4. idle_connection_timeout: This parameter specifies the duration an idle (keep-alive) connection stays open. If set to "0s", there’s no limit, allowing connections to remain idle indefinitely.
  5. max_idle_connections: It dictates the total number of idle (keep-alive) connections across all hosts. A setting of 0 implies no limit, potentially increasing resource usage but also readiness for incoming requests.

The HTTP transport settings documentation provides an in-depth exploration and will guide you through the process of adjusting these parameters for optimal API performance.

Performance Impacts of Keep-Alive Settings

Configuring these parameters impacts API performance significantly. Optimal keep-alive settings reduce latency as connections are reused, leading to faster response times for users. For servers, it means less CPU and memory consumption, enhancing system efficiency. However, the challenge lies in balancing these settings to avoid resource exhaustion, especially in high-traffic environments.

Challenges and Best Practices

Managing keep-alive connections is a balancing act. Aggressive keep-alive settings, while beneficial in maintaining connection readiness, can lead to resource exhaustion. Conversely, overly conservative settings may negate the performance benefits of keep-alive. The key is to monitor and adjust these settings in line with real-world usage patterns. Employing tools for performance monitoring can aid in this optimization process, ensuring that API performance is maximized without compromising resource efficiency.


In conclusion, keep-alive connection management in KrakenD is a potent tool for optimizing API performance. Understanding and configuring these parameters appropriately is essential for ensuring performant and resource-efficient APIs. As with any optimization, the process requires continuous monitoring and adjustments to maintain peak performance.

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