diff --git a/backend/ResQueue/ResQueue/Dtos/Broker/BrokerInvitationDto.cs b/backend/ResQueue/ResQueue/Dtos/Broker/BrokerInvitationDto.cs
index b48a434..02398df 100644
--- a/backend/ResQueue/ResQueue/Dtos/Broker/BrokerInvitationDto.cs
+++ b/backend/ResQueue/ResQueue/Dtos/Broker/BrokerInvitationDto.cs
@@ -2,13 +2,13 @@ namespace ResQueue.Dtos.Broker;
 
 public class BrokerInvitationDto
 {
-    public string Id { get; set; }
-    public string BrokerId { get; set; }
-    public string InviterId { get; set; }
-    public string InviteeId { get; set; }
-    public string InviterEmail { get; set; }
-    public string Token { get; set; }
-    public string BrokerName { get; set; }
+    public string Id { get; set; } = null!;
+    public string BrokerId { get; set; } = null!;
+    public string InviterId { get; set; } = null!;
+    public string InviteeId { get; set; } = null!;
+    public string InviterEmail { get; set; } = null!;
+    public string Token { get; set; } = null!;
+    public string BrokerName { get; set; } = null!;
     public DateTime CreatedAt { get; set; }
     public DateTime ExpiresAt { get; set; }
     public bool IsAccepted { get; set; }
diff --git a/backend/ResQueue/ResQueue/Dtos/ExchangeDto.cs b/backend/ResQueue/ResQueue/Dtos/ExchangeDto.cs
index e9a3af2..9e18d7e 100644
--- a/backend/ResQueue/ResQueue/Dtos/ExchangeDto.cs
+++ b/backend/ResQueue/ResQueue/Dtos/ExchangeDto.cs
@@ -2,6 +2,6 @@ namespace ResQueue.Dtos;
 
 public class ExchangeDto
 {
-    public string Id { get; set; }
-    public string RawData { get; set; }
+    public string Id { get; set; } = null!;
+    public string RawData { get; set; } = null!;
 }
\ No newline at end of file
diff --git a/backend/ResQueue/ResQueue/Dtos/MessageDto.cs b/backend/ResQueue/ResQueue/Dtos/MessageDto.cs
index 6dc5f96..79be25d 100644
--- a/backend/ResQueue/ResQueue/Dtos/MessageDto.cs
+++ b/backend/ResQueue/ResQueue/Dtos/MessageDto.cs
@@ -4,13 +4,13 @@ namespace ResQueue.Dtos;
 
 public class MessageDto
 {
-    public string Id { get; set; }
-    public JsonNode Body { get; set; }
+    public string Id { get; set; } = null!;
+    public JsonNode Body { get; set; } = null!;
 
     /// <summary>
     ///  "json" or "base64"
     /// </summary>
-    public string BodyEncoding { get; set; }
+    public string BodyEncoding { get; set; } = null!;
 
     public RabbitmqMessageMetadataDto? RabbitmqMetadata { get; set; }
     public bool IsReviewed { get; set; }
diff --git a/backend/ResQueue/ResQueue/Dtos/QueueDto.cs b/backend/ResQueue/ResQueue/Dtos/QueueDto.cs
index ecde7c6..b34a1c8 100644
--- a/backend/ResQueue/ResQueue/Dtos/QueueDto.cs
+++ b/backend/ResQueue/ResQueue/Dtos/QueueDto.cs
@@ -2,8 +2,8 @@ namespace ResQueue.Dtos;
 
 public class QueueDto
 {
-    public string Id { get; set; }
-    public string RawData { get; set; }
+    public string Id { get; set; } = null!;
+    public string RawData { get; set; } = null!;
     public long TotalMessages { get; set; }
     public bool IsFavorite { get; set; }
     public DateTime CreatedAt { get; set; }
diff --git a/backend/ResQueue/ResQueue/Dtos/UpsertMessageDto.cs b/backend/ResQueue/ResQueue/Dtos/UpsertMessageDto.cs
index 2f037f6..d2bc5a2 100644
--- a/backend/ResQueue/ResQueue/Dtos/UpsertMessageDto.cs
+++ b/backend/ResQueue/ResQueue/Dtos/UpsertMessageDto.cs
@@ -4,14 +4,14 @@ namespace ResQueue.Dtos;
 
 public class UpsertMessageDto
 {
-    public string BrokerId { get; set; }
-    public string QueueId { get; set; }
-    public JsonNode Body { get; set; }
+    public string BrokerId { get; set; } = null!;
+    public string QueueId { get; set; } = null!;
+    public JsonNode Body { get; set; } = null!;
 
     /// <summary>
     ///  "json" or "base64"
     /// </summary>
-    public string BodyEncoding { get; set; }
+    public string BodyEncoding { get; set; } = null!;
 
     public RabbitmqUpsertMessageMetadataDto? RabbitmqMetadata { get; set; }
 }
\ No newline at end of file
diff --git a/backend/ResQueue/ResQueue/Models/BrokerInvitation.cs b/backend/ResQueue/ResQueue/Models/BrokerInvitation.cs
index bda1b2b..be3ee52 100644
--- a/backend/ResQueue/ResQueue/Models/BrokerInvitation.cs
+++ b/backend/ResQueue/ResQueue/Models/BrokerInvitation.cs
@@ -7,11 +7,11 @@ public class BrokerInvitation
 {
     [BsonId] public ObjectId Id { get; set; }
     public ObjectId BrokerId { get; set; }
-    public ObjectId InviterId { get; set; } // User who invited
-    public ObjectId InviteeId { get; set; } // User who was invited
-    public string InviterEmail { get; set; }
-    public string Token { get; set; }
-    public string BrokerName { get; set; }
+    public ObjectId InviterId { get; set; }
+    public ObjectId InviteeId { get; set; }
+    public string InviterEmail { get; set; } = null!;
+    public string Token { get; set; } = null!;
+    public string BrokerName { get; set; } = null!;
     public DateTime CreatedAt { get; set; }
     public DateTime ExpiresAt { get; set; }
     public bool IsAccepted { get; set; } = false;
diff --git a/backend/ResQueue/ResQueue/Models/Exchange.cs b/backend/ResQueue/ResQueue/Models/Exchange.cs
index de737e9..8ffaaa2 100644
--- a/backend/ResQueue/ResQueue/Models/Exchange.cs
+++ b/backend/ResQueue/ResQueue/Models/Exchange.cs
@@ -8,5 +8,5 @@ public class Exchange
     [BsonId] public ObjectId Id { get; set; }
     public ObjectId UserId { get; set; }
     public ObjectId BrokerId { get; set; }
-    public BsonDocument RawData { get; set; }
+    public BsonDocument RawData { get; set; } = null!;
 }
\ No newline at end of file
diff --git a/backend/ResQueue/ResQueue/Models/Queue.cs b/backend/ResQueue/ResQueue/Models/Queue.cs
index 2ab26ab..b06331c 100644
--- a/backend/ResQueue/ResQueue/Models/Queue.cs
+++ b/backend/ResQueue/ResQueue/Models/Queue.cs
@@ -9,7 +9,7 @@ public class Queue
     public ObjectId BrokerId { get; set; }
     public int TotalMessages { get; set; }
     public bool IsFavorite { get; set; }
-    public BsonDocument RawData { get; set; }
+    public BsonDocument RawData { get; set; } = null!;
     public DateTime CreatedAt { get; set; }
     public long NextMessageOrder { get; set; }
 }
\ No newline at end of file
diff --git a/backend/ResQueue/ResQueue/PaginatedResult.cs b/backend/ResQueue/ResQueue/PaginatedResult.cs
index 980d680..b8d04f7 100644
--- a/backend/ResQueue/ResQueue/PaginatedResult.cs
+++ b/backend/ResQueue/ResQueue/PaginatedResult.cs
@@ -2,7 +2,7 @@ namespace ResQueue;
 
 public class PaginatedResult<T>
 {
-    public List<T> Items { get; set; }
+    public List<T> Items { get; set; } = null!;
     public int PageIndex { get; set; }
     public int TotalPages { get; set; }
     public int PageSize { get; set; }
diff --git a/backend/ResQueue/ResQueue/Settings.cs b/backend/ResQueue/ResQueue/Settings.cs
index 5ee10f8..a2ab3be 100644
--- a/backend/ResQueue/ResQueue/Settings.cs
+++ b/backend/ResQueue/ResQueue/Settings.cs
@@ -2,13 +2,13 @@ namespace ResQueue;
 
 public class Settings
 {
-    public string SmtpHost { get; set; }
+    public string SmtpHost { get; set; } = null!;
     public int SmtpPort { get; set; }
-    public string SmtpUsername { get; set; }
-    public string SmtpPassword { get; set; }
+    public string SmtpUsername { get; set; } = null!;
+    public string SmtpPassword { get; set; } = null!;
 
-    public string MongoDBConnectionString { get; set; }
+    public string MongoDBConnectionString { get; set; } = null!;
 
-    public string StripeSecret { get; set; }
-    public string StripeSecretWebhook { get; set; }
+    public string StripeSecret { get; set; } = null!;
+    public string StripeSecretWebhook { get; set; } = null!;
 }
\ No newline at end of file
diff --git a/backend/ResQueue/ResQueue/UserAvatarGenerator.cs b/backend/ResQueue/ResQueue/UserAvatarGenerator.cs
index b8ef8f7..81a1df0 100644
--- a/backend/ResQueue/ResQueue/UserAvatarGenerator.cs
+++ b/backend/ResQueue/ResQueue/UserAvatarGenerator.cs
@@ -33,7 +33,7 @@ public static class UserAvatarGenerator
         // Thread-safe random number generator
         private static readonly Random GlobalRandom = new Random();
         [ThreadStatic]
-        private static Random _localRandom;
+        private static Random? _localRandom;
 
         /// <summary>
         /// Generates an avatar with a random color from the predefined array and a random pattern.