What methods can be used to increase the performance and stability of a service under high load?

To improve the performance and stability of a service under high load, the following approaches can be used:

• Caching: storing frequently requested data in memory for quick access.
• Load balancing: distributing requests among multiple servers.
• Scaling: vertical (increasing resources of a single server) or horizontal (adding new servers).
• Asynchronous processing: using message queues and background tasks to offload main threads.
• Code and query optimization: reducing operation execution time.
• Using connection pools for databases and other resources.
• Monitoring and automatic recovery: tracking service status and restarting in case of failures.

Example in Java: using thread pools and caching with ConcurrentHashMap.

ExecutorService executor = Executors.newFixedThreadPool(10);
ConcurrentHashMap<String, String> cache = new ConcurrentHashMap<>();

public String getData(String key) {
    return cache.computeIfAbsent(key, k -> loadDataFromDB(k));
}

// Handling requests
executor.submit(() -> {
    String result = getData("someKey");
    // process the result
});