Initial commit carried over from private repo. This is V2.

code/MessengerApi.Db/Repositories/MessageRepository.cs

@@ -0,0 +1,23 @@
+using MessengerApi.Db.Contracts.Repositories;
+using MessengerApi.Db.Entities;
+using Microsoft.EntityFrameworkCore;
+
+namespace MessengerApi.Db.Repositories
+{
+    public class MessageRepository : Repository<Message>, IMessageRepository
+    {
+        public MessageRepository(DbSet<Message> db) : base(db)
+        {
+        }
+
+        public IEnumerable<Message> GetPendingMessages(User user)
+        {
+            var timestamp = DateTime.UtcNow;
+
+            return this.db
+                .Where(x => x.ToId == user.Id && x.IsDelivered == false)
+                .Where(x => x.PayloadLifespanInSeconds == null || x.CreatedUtc.AddSeconds(x.PayloadLifespanInSeconds.Value) >= timestamp)
+                .OrderBy(x => x.CreatedUtc);
+        }
+    }
+}