Renting reusable buffer arrays in high-throughput network and file I/O:

byte[] buffer = ArrayPool<byte>.Shared.Rent(65536); // Rent 64KB buffer
try
{
    int bytesRead = await stream.ReadAsync(buffer.AsMemory(0, 65536));
    ProcessData(buffer.AsSpan(0, bytesRead));
}
finally
{
    ArrayPool<byte>.Shared.Return(buffer); // Return to pool for reuse!
}

Key Rule: Remember that rented arrays may be larger than requested (Rent(1000) might return a 1024-byte array). Always slice by actual length (buffer.AsSpan(0, bytesRead))!

ArrayPool<T>.Shared completely eliminates heap allocation churn in HTTP handlers and WebSocket servers.

Pass clearArray: true when returning buffers that contained sensitive data like passwords or crypto keys to prevent memory leakage.