1,000,000 IDs per second for approximately 136 years

GuidGenerator.cs

using System;
using System.Security.Cryptography;
using System.Text;

public class GuidGenerator
{
    private static readonly object LockObject = new object();
    private static int _sequenceNumber = 0;
    private readonly string _serverId;

    public GuidGenerator(string serverId)
    {
        _serverId = serverId;
    }

    public string GenerateGuid()
    {
        lock (LockObject)
        {
            // Get current timestamp
            long timestamp = DateTimeOffset.UtcNow.ToUnixTimeMilliseconds();

            // Increment sequence number
            _sequenceNumber = (_sequenceNumber + 1) % 1000; // Example sequence within the same millisecond

            // Generate random part
            byte[] randomBytes = new byte[4];
            using (var rng = RandomNumberGenerator.Create())
            {
                rng.GetBytes(randomBytes);
            }
            string randomPart = BitConverter.ToString(randomBytes).Replace("-", "");

            // Combine parts
            string guid = $"{timestamp}-{_serverId}-{_sequenceNumber:D3}-{randomPart}";
            return guid;
        }
    }
}