feat: optimize TTFB with lazy DB init and newsletter caching

server.py

@@ -15,7 +15,92 @@ SMTP_USER     = os.getenv('SMTP_USER')
 SMTP_PASSWORD = os.getenv('SMTP_PASSWORD')
 
 app = Flask(__name__)
-init_db()
+
+_db_initialized = False
+_newsletter_cache = {}
+_cache_timestamp = {}
+CACHE_DURATION = 300
+
+def ensure_db_initialized():
+    """Lazy database initialization - only runs on first database access"""
+    global _db_initialized
+    if not _db_initialized:
+        init_db()
+        _db_initialized = True
+
+def get_newsletters_cached():
+    """Get newsletters with caching to reduce database hits"""
+    current_time = time.time()
+    
+    if ('newsletters' in _newsletter_cache and 
+        current_time - _cache_timestamp.get('newsletters', 0) < CACHE_DURATION):
+        return _newsletter_cache['newsletters']
+    
+    ensure_db_initialized()
+    conn = get_connection()
+    cursor = conn.cursor()
+    cursor.execute(
+        "SELECT id, subject, body, sent_at "
+        "FROM newsletters ORDER BY sent_at DESC"
+    )
+    rows = cursor.fetchall()
+    cursor.close()
+    conn.close()
+    
+    newsletters = [
+        {"id": r[0], "subject": r[1], "body": r[2], "sent_at": r[3]}
+        for r in rows
+    ]
+    
+    _newsletter_cache['newsletters'] = newsletters
+    _cache_timestamp['newsletters'] = current_time
+    
+    return newsletters
+
+def get_newsletter_by_id_cached(newsletter_id):
+    """Get single newsletter with caching"""
+    cache_key = f'newsletter_{newsletter_id}'
+    current_time = time.time()
+    
+    if (cache_key in _newsletter_cache and 
+        current_time - _cache_timestamp.get(cache_key, 0) < CACHE_DURATION):
+        return _newsletter_cache[cache_key]
+    
+    ensure_db_initialized()
+    conn = get_connection()
+    cursor = conn.cursor()
+    cursor.execute(
+        "SELECT id, subject, body, sent_at "
+        "FROM newsletters WHERE id = %s",
+        (newsletter_id,)
+    )
+    row = cursor.fetchone()
+    cursor.close()
+    conn.close()
+    
+    if not row:
+        return None
+        
+    newsletter = {
+        "id": row[0],
+        "subject": row[1],
+        "body": row[2],
+        "sent_at": row[3]
+    }
+    
+    _newsletter_cache[cache_key] = newsletter
+    _cache_timestamp[cache_key] = current_time
+    
+    return newsletter
+
+def clear_newsletter_cache():
+    """Clear newsletter cache when data is updated"""
+    global _newsletter_cache, _cache_timestamp
+    keys_to_remove = [k for k in _newsletter_cache.keys() 
+                      if k.startswith('newsletter')]
+    for key in keys_to_remove:
+        _newsletter_cache.pop(key, None)
+        _cache_timestamp.pop(key, None)
 
 @app.before_request
 def start_timer():
@@ -58,15 +143,19 @@ def send_confirmation_async(email, unsubscribe_link):
 
 @app.route("/", methods=["GET"])
 def index():
+    """Home page - no database access needed"""
     return render_template("index.html")
 
 @app.route("/subscribe", methods=["POST"])
 def subscribe():
+    """Subscribe endpoint - lazy loads database only when needed"""
     data = request.get_json() or {}
     email = data.get("email")
     if not email:
         return jsonify(error="No email provided"), 400
 
+    ensure_db_initialized()
+    
     if add_email(email):
         unsubscribe_link = f"{request.url_root}unsubscribe?email={email}"
 
@@ -82,63 +171,42 @@ def subscribe():
 
 @app.route("/unsubscribe", methods=["GET"])
 def unsubscribe():
+    """Unsubscribe endpoint - lazy loads database only when needed"""
     email = request.args.get("email")
     if not email:
         return "No email specified.", 400
 
+    ensure_db_initialized()
+    
     if remove_email(email):
         return f"The email {email} has been unsubscribed.", 200
     return f"Email {email} was not found or has already been unsubscribed.", 400
 
-
 @app.route("/newsletters", methods=["GET"])
 def newsletters():
     """
-    List all newsletters (newest first).
+    List all newsletters (newest first) with caching for better performance.
     """
-    conn   = get_connection()
-    cursor = conn.cursor()
-    cursor.execute(
-        "SELECT id, subject, body, sent_at "
-      + "FROM newsletters ORDER BY sent_at DESC"
-    )
-    rows = cursor.fetchall()
-    cursor.close()
-    conn.close()
-
-    newsletters = [
-        {"id": r[0], "subject": r[1], "body": r[2], "sent_at": r[3]}
-        for r in rows
-    ]
+    newsletters = get_newsletters_cached()
     return render_template("newsletters.html", newsletters=newsletters)
 
-
 @app.route("/newsletter/<int:newsletter_id>", methods=["GET"])
 def newsletter_detail(newsletter_id):
     """
-    Show a single newsletter by its ID.
+    Show a single newsletter by its ID with caching.
     """
-    conn   = get_connection()
-    cursor = conn.cursor()
-    cursor.execute(
-        "SELECT id, subject, body, sent_at "
-      + "FROM newsletters WHERE id = %s",
-        (newsletter_id,)
-    )
-    row = cursor.fetchone()
-    cursor.close()
-    conn.close()
-
-    if not row:
+    newsletter = get_newsletter_by_id_cached(newsletter_id)
+    
+    if not newsletter:
         return "Newsletter not found.", 404
 
-    newsletter = {
-        "id":      row[0],
-        "subject": row[1],
-        "body":    row[2],
-        "sent_at": row[3]
-    }
     return render_template("newsletter_detail.html", newsletter=newsletter)
 
+@app.route("/admin/clear-cache", methods=["POST"])
+def clear_cache():
+    """Admin endpoint to clear newsletter cache"""
+    clear_newsletter_cache()
+    return jsonify(message="Cache cleared successfully"), 200
+
 if __name__ == "__main__":
     app.run(host="0.0.0.0", debug=True)