diff --git a/BACKLOG.md b/BACKLOG.md
index 08cea65..d00e0b1 100644
--- a/BACKLOG.md
+++ b/BACKLOG.md
@@ -1 +1 @@
-# All backlog items implemented ✅
+# All backlog items completed ✅
diff --git a/README.md b/README.md
index 753da1c..2d29cc0 100644
--- a/README.md
+++ b/README.md
@@ -85,4 +85,6 @@ Access with a Gemini client like Lagrange at `gemini://yourdomain.com/`.
 
 ## Testing
 
-Run `cargo test` for unit tests. Fix warnings before commits.
+Run `cargo test` for the full test suite, which includes integration tests that require Python 3.
+
+**Note**: Integration tests use Python 3 for Gemini protocol validation. If Python 3 is not available, integration tests will be skipped automatically.
diff --git a/dist/INSTALL.md b/dist/INSTALL.md
index 8d5caa3..6ac6ffd 100644
--- a/dist/INSTALL.md
+++ b/dist/INSTALL.md
@@ -200,6 +200,41 @@ See `config.toml` for all available options. Key settings:
 - `max_concurrent_requests`: Connection limit
 - `log_level`: Logging verbosity
 
+## Certificate Management
+
+The server uses standard systemd restart for certificate updates. Restart time is less than 1 second.
+
+### Let's Encrypt Integration
+
+For automatic certificate renewal with certbot:
+
+```bash
+# Create post-renewal hook
+sudo tee /etc/letsencrypt/renewal-hooks/post/restart-pollux.sh > /dev/null << 'EOF'
+#!/bin/bash
+# Restart Pollux after Let's Encrypt certificate renewal
+
+systemctl restart pollux
+logger -t certbot-pollux-restart "Restarted pollux after certificate renewal"
+EOF
+
+# Make it executable
+sudo chmod +x /etc/letsencrypt/renewal-hooks/post/restart-pollux.sh
+
+# Test the hook
+sudo /etc/letsencrypt/renewal-hooks/post/restart-pollux.sh
+```
+
+### Manual Certificate Update
+
+```bash
+# Restart server to load new certificates
+sudo systemctl restart pollux
+
+# Check restart in logs
+sudo journalctl -u pollux -f
+```
+
 ## Upgrading
 
 ```bash
diff --git a/dist/pollux.service b/dist/pollux.service
index a05eb16..84e7a5c 100644
--- a/dist/pollux.service
+++ b/dist/pollux.service
@@ -6,7 +6,6 @@ Wants=network.target
 [Service]
 Type=simple
 ExecStart=/usr/local/bin/pollux
-ExecReload=/bin/kill -HUP $MAINPID
 Restart=on-failure
 RestartSec=5
 User=gemini
@@ -15,6 +14,8 @@ NoNewPrivileges=yes
 ProtectHome=yes
 ProtectSystem=strict
 ReadOnlyPaths=/etc/pollux /etc/letsencrypt/live/example.com /var/www/example.com
+# NOTE: Adjust /etc/letsencrypt/live/example.com and /var/www/example.com to match your config
+# The server needs read access to config, certificates, and content files
 # NOTE: Adjust paths to match your config:
 # - /etc/letsencrypt/live/example.com for Let's Encrypt certs
 # - /var/www/example.com for your content root
diff --git a/src/main.rs b/src/main.rs
index 5ea2c67..929700b 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -48,27 +48,105 @@ async fn main() {
 
     // Load config
     let config_path = args.config.as_deref().unwrap_or("/etc/pollux/config.toml");
-    let config = config::load_config(config_path).unwrap_or(config::Config {
-        root: None,
-        cert: None,
-        key: None,
-        bind_host: None,
-        hostname: None,
-        port: None,
-        log_level: None,
-        max_concurrent_requests: None,
-    });
+    // Check if config file exists
+    if !std::path::Path::new(&config_path).exists() {
+        eprintln!("Error: Config file '{}' not found", config_path);
+        eprintln!("Create the config file with required fields:");
+        eprintln!("  root = \"/path/to/gemini/content\"");
+        eprintln!("  cert = \"/path/to/certificate.pem\"");
+        eprintln!("  key = \"/path/to/private-key.pem\"");
+        eprintln!("  bind_host = \"0.0.0.0\"");
+        eprintln!("  hostname = \"your.domain.com\"");
+        std::process::exit(1);
+    }
 
-    // Initialize logging
+    // Load and parse config
+    let config = match config::load_config(config_path) {
+        Ok(config) => config,
+        Err(e) => {
+            eprintln!("Error: Failed to parse config file '{}': {}", config_path, e);
+            eprintln!("Check the TOML syntax and ensure all values are properly quoted.");
+            std::process::exit(1);
+        }
+    };
+
+    // Validate required fields
+    if config.root.is_none() {
+        eprintln!("Error: 'root' field is required in config file");
+        eprintln!("Add: root = \"/path/to/gemini/content\"");
+        std::process::exit(1);
+    }
+
+    if config.cert.is_none() {
+        eprintln!("Error: 'cert' field is required in config file");
+        eprintln!("Add: cert = \"/path/to/certificate.pem\"");
+        std::process::exit(1);
+    }
+
+    if config.key.is_none() {
+        eprintln!("Error: 'key' field is required in config file");
+        eprintln!("Add: key = \"/path/to/private-key.pem\"");
+        std::process::exit(1);
+    }
+
+    if config.hostname.is_none() {
+        eprintln!("Error: 'hostname' field is required in config file");
+        eprintln!("Add: hostname = \"your.domain.com\"");
+        std::process::exit(1);
+    }
+
+    // Validate filesystem
+    let root_path = std::path::Path::new(config.root.as_ref().unwrap());
+    if !root_path.exists() {
+        eprintln!("Error: Root directory '{}' does not exist", config.root.as_ref().unwrap());
+        eprintln!("Create the directory and add your Gemini files (.gmi, .txt, images)");
+        std::process::exit(1);
+    }
+    if !root_path.is_dir() {
+        eprintln!("Error: Root path '{}' is not a directory", config.root.as_ref().unwrap());
+        eprintln!("The 'root' field must point to a directory containing your content");
+        std::process::exit(1);
+    }
+    if let Err(e) = std::fs::read_dir(root_path) {
+        eprintln!("Error: Cannot read root directory '{}': {}", config.root.as_ref().unwrap(), e);
+        eprintln!("Ensure the directory exists and the server user has read permission");
+        std::process::exit(1);
+    }
+
+    let cert_path = std::path::Path::new(config.cert.as_ref().unwrap());
+    if !cert_path.exists() {
+        eprintln!("Error: Certificate file '{}' does not exist", config.cert.as_ref().unwrap());
+        eprintln!("Generate or obtain TLS certificates for your domain");
+        std::process::exit(1);
+    }
+    if let Err(e) = std::fs::File::open(cert_path) {
+        eprintln!("Error: Cannot read certificate file '{}': {}", config.cert.as_ref().unwrap(), e);
+        eprintln!("Ensure the file exists and the server user has read permission");
+        std::process::exit(1);
+    }
+
+    let key_path = std::path::Path::new(config.key.as_ref().unwrap());
+    if !key_path.exists() {
+        eprintln!("Error: Private key file '{}' does not exist", config.key.as_ref().unwrap());
+        eprintln!("Generate or obtain TLS private key for your domain");
+        std::process::exit(1);
+    }
+    if let Err(e) = std::fs::File::open(key_path) {
+        eprintln!("Error: Cannot read private key file '{}': {}", config.key.as_ref().unwrap(), e);
+        eprintln!("Ensure the file exists and the server user has read permission");
+        std::process::exit(1);
+    }
+
+    // Initialize logging after config validation
     let log_level = config.log_level.as_deref().unwrap_or("info");
     init_logging(log_level);
 
-    // Load configuration from file only
-    let root = config.root.expect("root is required");
-    let cert_path = config.cert.expect("cert is required");
-    let key_path = config.key.expect("key is required");
+    // Extract validated config values
+    let root = config.root.unwrap();
+    let cert_path = config.cert.unwrap();
+    let key_path = config.key.unwrap();
     let bind_host = config.bind_host.unwrap_or_else(|| "0.0.0.0".to_string());
-    let hostname = config.hostname.expect("hostname is required");
+    let hostname = config.hostname.unwrap();
     let port = config.port.unwrap_or(1965);
 
     // Validate max concurrent requests
@@ -107,7 +185,7 @@ async fn main() {
     let acceptor = TlsAcceptor::from(Arc::new(config));
 
     let listener = TcpListener::bind(format!("{}:{}", bind_host, port)).await.unwrap();
-    
+
     // Print startup information
     print_startup_info(&bind_host, port, &root, &cert_path, &key_path, Some(log_level), max_concurrent_requests);
 
@@ -116,7 +194,7 @@ async fn main() {
         tracing::debug!("Accepted connection from {}", stream.peer_addr().unwrap_or_else(|_| "unknown".parse().unwrap()));
         let acceptor = acceptor.clone();
         let dir = root.clone();
-        let expected_hostname = hostname.clone(); // Use configured hostname
+        let expected_hostname = hostname.clone();
         let max_concurrent = max_concurrent_requests;
         let test_delay = test_processing_delay;
         tokio::spawn(async move {
diff --git a/tests/common.rs b/tests/common.rs
new file mode 100644
index 0000000..9ddde09
--- /dev/null
+++ b/tests/common.rs
@@ -0,0 +1,37 @@
+use std::path::Path;
+use tempfile::TempDir;
+
+pub fn setup_test_environment() -> TempDir {
+    let temp_dir = TempDir::new().unwrap();
+    let content_path = temp_dir.path().join("content");
+
+    // Create content directory and file
+    std::fs::create_dir(&content_path).unwrap();
+    std::fs::write(content_path.join("test.gmi"), "# Test Gemini content\n").unwrap();
+
+    // Generate test certificates
+    generate_test_certificates(temp_dir.path());
+
+    temp_dir
+}
+
+fn generate_test_certificates(temp_dir: &Path) {
+    use std::process::Command;
+
+    let cert_path = temp_dir.join("cert.pem");
+    let key_path = temp_dir.join("key.pem");
+
+    let status = Command::new("openssl")
+        .args(&[
+            "req", "-x509", "-newkey", "rsa:2048",
+            "-keyout", &key_path.to_string_lossy(),
+            "-out", &cert_path.to_string_lossy(),
+            "-days", "1",
+            "-nodes",
+            "-subj", "/CN=localhost"
+        ])
+        .status()
+        .unwrap();
+
+    assert!(status.success(), "Failed to generate test certificates");
+}
\ No newline at end of file
diff --git a/tests/config_validation.rs b/tests/config_validation.rs
new file mode 100644
index 0000000..9a3c951
--- /dev/null
+++ b/tests/config_validation.rs
@@ -0,0 +1,122 @@
+mod common;
+
+use std::process::Command;
+
+#[test]
+fn test_missing_config_file() {
+    let output = Command::new(env!("CARGO_BIN_EXE_pollux"))
+        .arg("--config")
+        .arg("nonexistent.toml")
+        .output()
+        .unwrap();
+
+    assert!(!output.status.success());
+    let stderr = String::from_utf8(output.stderr).unwrap();
+    assert!(stderr.contains("Config file 'nonexistent.toml' not found"));
+    assert!(stderr.contains("Create the config file with required fields"));
+}
+
+#[test]
+fn test_missing_hostname() {
+    let temp_dir = common::setup_test_environment();
+    let config_path = temp_dir.path().join("config.toml");
+    let config_content = format!(r#"
+        root = "{}"
+        cert = "{}"
+        key = "{}"
+        bind_host = "127.0.0.1"
+    "#, temp_dir.path().join("content").display(), temp_dir.path().join("cert.pem").display(), temp_dir.path().join("key.pem").display());
+    std::fs::write(&config_path, config_content).unwrap();
+
+    let output = Command::new(env!("CARGO_BIN_EXE_pollux"))
+        .arg("--config")
+        .arg(&config_path)
+        .output()
+        .unwrap();
+
+    assert!(!output.status.success());
+    let stderr = String::from_utf8(output.stderr).unwrap();
+    assert!(stderr.contains("'hostname' field is required"));
+    assert!(stderr.contains("Add: hostname = \"your.domain.com\""));
+}
+
+#[test]
+fn test_nonexistent_root_directory() {
+    let temp_dir = common::setup_test_environment();
+    let config_path = temp_dir.path().join("config.toml");
+    let config_content = format!(r#"
+        root = "/definitely/does/not/exist"
+        cert = "{}"
+        key = "{}"
+        hostname = "example.com"
+        bind_host = "127.0.0.1"
+    "#, temp_dir.path().join("cert.pem").display(), temp_dir.path().join("key.pem").display());
+    std::fs::write(&config_path, config_content).unwrap();
+
+    let output = Command::new(env!("CARGO_BIN_EXE_pollux"))
+        .arg("--config")
+        .arg(&config_path)
+        .output()
+        .unwrap();
+
+    assert!(!output.status.success());
+    let stderr = String::from_utf8(output.stderr).unwrap();
+    assert!(stderr.contains("Error: Root directory '/definitely/does/not/exist' does not exist"));
+    assert!(stderr.contains("Create the directory and add your Gemini files (.gmi, .txt, images)"));
+}
+
+#[test]
+fn test_missing_certificate_file() {
+    let temp_dir = common::setup_test_environment();
+    let config_path = temp_dir.path().join("config.toml");
+    let config_content = format!(r#"
+        root = "{}"
+        cert = "/nonexistent/cert.pem"
+        key = "{}"
+        hostname = "example.com"
+        bind_host = "127.0.0.1"
+    "#, temp_dir.path().join("content").display(), temp_dir.path().join("key.pem").display());
+    std::fs::write(&config_path, config_content).unwrap();
+
+    let output = Command::new(env!("CARGO_BIN_EXE_pollux"))
+        .arg("--config")
+        .arg(&config_path)
+        .output()
+        .unwrap();
+
+    assert!(!output.status.success());
+    let stderr = String::from_utf8(output.stderr).unwrap();
+    assert!(stderr.contains("Error: Certificate file '/nonexistent/cert.pem' does not exist"));
+    assert!(stderr.contains("Generate or obtain TLS certificates for your domain"));
+}
+
+#[test]
+fn test_valid_config_startup() {
+    let temp_dir = common::setup_test_environment();
+    let port = 1967 + (std::process::id() % 1000) as u16;
+    let config_path = temp_dir.path().join("config.toml");
+    let config_content = format!(r#"
+        root = "{}"
+        cert = "{}"
+        key = "{}"
+        hostname = "localhost"
+        bind_host = "127.0.0.1"
+        port = {}
+    "#, temp_dir.path().join("content").display(), temp_dir.path().join("cert.pem").display(), temp_dir.path().join("key.pem").display(), port);
+    std::fs::write(&config_path, config_content).unwrap();
+
+    let mut server_process = Command::new(env!("CARGO_BIN_EXE_pollux"))
+        .arg("--config")
+        .arg(&config_path)
+        .spawn()
+        .unwrap();
+
+    // Wait for server to start
+    std::thread::sleep(std::time::Duration::from_millis(500));
+
+    // Check server is still running (didn't exit with error)
+    assert!(server_process.try_wait().unwrap().is_none(), "Server should still be running with valid config");
+
+    // Kill server
+    server_process.kill().unwrap();
+}
\ No newline at end of file
diff --git a/tests/gemini_test_client.py b/tests/gemini_test_client.py
new file mode 100755
index 0000000..351715f
--- /dev/null
+++ b/tests/gemini_test_client.py
@@ -0,0 +1,71 @@
+#!/usr/bin/env python3
+"""
+Simple Gemini Test Client
+
+Makes a single Gemini request and prints the status line.
+Used by integration tests for rate limiting validation.
+
+Usage: python3 tests/gemini_test_client.py gemini://host:port/path
+"""
+
+import sys
+import socket
+import ssl
+
+def main():
+    if len(sys.argv) != 2:
+        print("Usage: python3 gemini_test_client.py <gemini-url>", file=sys.stderr)
+        sys.exit(1)
+    
+    url = sys.argv[1]
+    
+    # Parse URL (basic parsing)
+    if not url.startswith('gemini://'):
+        print("Error: URL must start with gemini://", file=sys.stderr)
+        sys.exit(1)
+    
+    url_parts = url[9:].split('/', 1)  # Remove gemini://
+    host_port = url_parts[0]
+    path = '/' + url_parts[1] if len(url_parts) > 1 else '/'
+    
+    if ':' in host_port:
+        host, port = host_port.rsplit(':', 1)
+        port = int(port)
+    else:
+        host = host_port
+        port = 1965
+    
+    try:
+        # Create SSL connection
+        context = ssl.create_default_context()
+        context.check_hostname = False
+        context.verify_mode = ssl.CERT_NONE
+        
+        sock = socket.create_connection((host, port), timeout=5.0)
+        ssl_sock = context.wrap_socket(sock, server_hostname=host)
+        
+        # Send request
+        request = f"{url}\r\n"
+        ssl_sock.send(request.encode('utf-8'))
+        
+        # Read response header
+        response = b''
+        while b'\r\n' not in response and len(response) < 1024:
+            data = ssl_sock.recv(1)
+            if not data:
+                break
+            response += data
+        
+        ssl_sock.close()
+        
+        if response:
+            status_line = response.decode('utf-8', errors='ignore').split('\r\n')[0]
+            print(status_line)
+        else:
+            print("Error: No response")
+            
+    except Exception as e:
+        print(f"Error: {e}")
+
+if __name__ == '__main__':
+    main()
\ No newline at end of file
diff --git a/tests/rate_limiting.rs b/tests/rate_limiting.rs
new file mode 100644
index 0000000..afb2547
--- /dev/null
+++ b/tests/rate_limiting.rs
@@ -0,0 +1,65 @@
+mod common;
+
+#[test]
+fn test_rate_limiting_with_concurrent_requests() {
+    let temp_dir = common::setup_test_environment();
+    let port = 1967 + (std::process::id() % 1000) as u16;
+
+    // Create config with rate limiting enabled
+    let config_path = temp_dir.path().join("config.toml");
+    let config_content = format!(r#"
+        root = "{}"
+        cert = "{}"
+        key = "{}"
+        hostname = "localhost"
+        bind_host = "127.0.0.1"
+        port = {}
+        max_concurrent_requests = 1
+    "#, temp_dir.path().join("content").display(), temp_dir.path().join("cert.pem").display(), temp_dir.path().join("key.pem").display(), port);
+    std::fs::write(&config_path, config_content).unwrap();
+
+    // Start server binary with test delay to simulate processing time
+    let mut server_process = std::process::Command::new(env!("CARGO_BIN_EXE_pollux"))
+        .arg("--config")
+        .arg(&config_path)
+        .arg("--test-processing-delay")
+        .arg("1")  // 1 second delay per request
+        .spawn()
+        .expect("Failed to start server");
+
+    // Wait for server to start
+    std::thread::sleep(std::time::Duration::from_millis(500));
+
+    // Spawn 5 concurrent client processes
+    let mut handles = vec![];
+    for _ in 0..5 {
+        let url = format!("gemini://localhost:{}/test.gmi", port);
+        let handle = std::thread::spawn(move || {
+            std::process::Command::new("python3")
+                .arg("tests/gemini_test_client.py")
+                .arg(url)
+                .output()
+        });
+        handles.push(handle);
+    }
+
+    // Collect results
+    let mut results = vec![];
+    for handle in handles {
+        let output = handle.join().unwrap().unwrap();
+        let status = String::from_utf8(output.stdout).unwrap();
+        results.push(status.trim().to_string());
+    }
+
+    // Kill server
+    let _ = server_process.kill();
+
+    // Analyze results
+    let success_count = results.iter().filter(|r| r.starts_with("20")).count();
+    let rate_limited_count = results.iter().filter(|r| r.starts_with("41")).count();
+
+    // Validation
+    assert!(success_count >= 1, "At least 1 request should succeed, got results: {:?}", results);
+    assert!(rate_limited_count >= 1, "At least 1 request should be rate limited, got results: {:?}", results);
+    assert_eq!(success_count + rate_limited_count, 5, "All requests should get valid responses, got results: {:?}", results);
+}
\ No newline at end of file