diff --git a/SchengenVisaApi/ApplicationLayer/CreateVisaApplicationRequest.cs b/SchengenVisaApi/ApplicationLayer/CreateVisaApplicationRequest.cs
index 80ce2b0..9885310 100644
--- a/SchengenVisaApi/ApplicationLayer/CreateVisaApplicationRequest.cs
+++ b/SchengenVisaApi/ApplicationLayer/CreateVisaApplicationRequest.cs
@@ -3,6 +3,7 @@ using Domains.VisaApplicationDomain;
 
 namespace ApplicationLayer;
 
+/// Model of visa request from user
 public record CreateVisaApplicationRequest(
     Name FullName,
     Passport Passport,
diff --git a/SchengenVisaApi/Domains/VisaApplicationDomain/VisaApplication.cs b/SchengenVisaApi/Domains/VisaApplicationDomain/VisaApplication.cs
index 1108852..3a51796 100644
--- a/SchengenVisaApi/Domains/VisaApplicationDomain/VisaApplication.cs
+++ b/SchengenVisaApi/Domains/VisaApplicationDomain/VisaApplication.cs
@@ -1,5 +1,4 @@
-using System.ComponentModel.DataAnnotations.Schema;
-using Domains.ApplicantDomain;
+using Domains.ApplicantDomain;
 using Domains.LocationDomain;
 
 namespace Domains.VisaApplicationDomain
@@ -14,7 +13,7 @@ namespace Domains.VisaApplicationDomain
         public Guid ApplicantId { get; set; }
 
         /// Applicant of <see cref="VisaApplication"/>
-        public Applicant Applicant { get; set; }
+        public Applicant Applicant { get; set; } = null!;
 
         /// <inheritdoc cref="Domains.VisaApplicationDomain.ReentryPermit"/>
         /// <remarks>always null if <see cref="Applicant"/> is not a non-resident</remarks>
diff --git a/SchengenVisaApi/Infrastructure/Database/Applicants/Repositories/ApplicantsRepository.cs b/SchengenVisaApi/Infrastructure/Database/Applicants/Repositories/ApplicantsRepository.cs
index a1e5170..473a43b 100644
--- a/SchengenVisaApi/Infrastructure/Database/Applicants/Repositories/ApplicantsRepository.cs
+++ b/SchengenVisaApi/Infrastructure/Database/Applicants/Repositories/ApplicantsRepository.cs
@@ -4,12 +4,16 @@ using Microsoft.EntityFrameworkCore;
 
 namespace Infrastructure.Database.Applicants.Repositories
 {
-    public class ApplicantsRepository(IGenericReader reader, IGenericWriter writer, IUnitOfWork unitOfWork)
-        : GenericRepository<Applicant>(writer, unitOfWork), IApplicantsRepository
+    /// Repository pattern for <see cref="Applicant"/>
+    /// <param name="reader"><inheritdoc cref="IGenericReader"/></param>
+    /// <param name="writer"><inheritdoc cref="IGenericWriter"/></param>
+    /// <param name="unitOfWork"><inheritdoc cref="IUnitOfWork"/></param>
+    public sealed class ApplicantsRepository(IGenericReader reader, IGenericWriter writer, IUnitOfWork unitOfWork)
+        : GenericRepository<Applicant>(reader, writer, unitOfWork), IApplicantsRepository
     {
         protected override IQueryable<Applicant> LoadDomain()
         {
-            return reader.GetAll<Applicant>()
+            return base.LoadDomain()
                 .Include(a => a.CountryOfBirth)
                 .Include(a => a.CityOfBirth)
                 .Include(a => a.PlaceOfWork);
diff --git a/SchengenVisaApi/Infrastructure/Database/Applicants/Repositories/IApplicantsRepository.cs b/SchengenVisaApi/Infrastructure/Database/Applicants/Repositories/IApplicantsRepository.cs
index fe1280c..d26b29a 100644
--- a/SchengenVisaApi/Infrastructure/Database/Applicants/Repositories/IApplicantsRepository.cs
+++ b/SchengenVisaApi/Infrastructure/Database/Applicants/Repositories/IApplicantsRepository.cs
@@ -3,5 +3,6 @@ using Infrastructure.Database.Generic;
 
 namespace Infrastructure.Database.Applicants.Repositories
 {
+    /// Repository pattern for <see cref="Applicant"/>
     public interface IApplicantsRepository : IGenericRepository<Applicant> { }
 }
diff --git a/SchengenVisaApi/Infrastructure/Database/GeneralExceptions/EntityNotFoundException.cs b/SchengenVisaApi/Infrastructure/Database/GeneralExceptions/EntityNotFoundException.cs
index 79e5a5a..d98221d 100644
--- a/SchengenVisaApi/Infrastructure/Database/GeneralExceptions/EntityNotFoundException.cs
+++ b/SchengenVisaApi/Infrastructure/Database/GeneralExceptions/EntityNotFoundException.cs
@@ -1,4 +1,10 @@
-namespace Infrastructure.Database.GeneralExceptions
+using Domains;
+
+namespace Infrastructure.Database.GeneralExceptions
 {
-    public class EntityNotFoundException<T>(Guid id) : Exception($"Entity {typeof(T).Name} with id '{id}' not found");
+    /// Exception to throw when entity with specific id not found
+    /// <param name="id">Identifier of entity</param>
+    /// <typeparam name="T">Not found entity type</typeparam>
+    public class EntityNotFoundException<T>(Guid id) : Exception($"Entity {typeof(T).Name} with id '{id}' not found")
+        where T : class, IEntity;
 }
diff --git a/SchengenVisaApi/Infrastructure/Database/Generic/GenericRepository.cs b/SchengenVisaApi/Infrastructure/Database/Generic/GenericRepository.cs
index 306dbde..c8c2391 100644
--- a/SchengenVisaApi/Infrastructure/Database/Generic/GenericRepository.cs
+++ b/SchengenVisaApi/Infrastructure/Database/Generic/GenericRepository.cs
@@ -4,35 +4,50 @@ using Microsoft.EntityFrameworkCore;
 
 namespace Infrastructure.Database.Generic
 {
-    public abstract class GenericRepository<T>(IGenericWriter writer, IUnitOfWork unitOfWork) : IGenericRepository<T>
+    /// Generic repository pattern
+    /// <param name="writer"><inheritdoc cref="IGenericWriter"/></param>
+    /// <param name="unitOfWork"><inheritdoc cref="IUnitOfWork"/></param>
+    /// <typeparam name="T">Type of entity</typeparam>
+    /// <remarks>Should be inherited to create typed repositories</remarks>
+    public abstract class GenericRepository<T>(IGenericReader reader, IGenericWriter writer, IUnitOfWork unitOfWork) : IGenericRepository<T>
         where T : class, IEntity
     {
+        /// <inheritdoc cref="IGenericRepository{T}.GetAllAsync"/>
         public async Task<List<T>> GetAllAsync(CancellationToken cancellationToken)
             => await LoadDomain().ToListAsync(cancellationToken);
 
+        /// <inheritdoc cref="IGenericRepository{T}.GetOneAsync"/>
         public async Task<T> GetOneAsync(Guid id, CancellationToken cancellationToken)
         {
             var result = await LoadDomain().SingleOrDefaultAsync(a => a.Id == id, cancellationToken);
             return result ?? throw new EntityNotFoundException<T>(id);
         }
 
+        /// <inheritdoc cref="IGenericRepository{T}.AddAsync"/>
         public async Task AddAsync(T entity, CancellationToken cancellationToken)
             => await writer.AddAsync(entity, cancellationToken);
 
+        /// <inheritdoc cref="IGenericRepository{T}.UpdateAsync"/>
         public async Task UpdateAsync(T entity, CancellationToken cancellationToken)
         {
             await GetOneAsync(entity.Id, cancellationToken);
             writer.Update(entity);
         }
 
+        /// <inheritdoc cref="IGenericRepository{T}.Remove"/>
         public void Remove(T entity)
         {
             writer.Remove(entity);
         }
 
+        /// <inheritdoc cref="IGenericRepository{T}.SaveAsync"/>
         public async Task SaveAsync(CancellationToken cancellationToken)
             => await unitOfWork.SaveAsync(cancellationToken);
 
-        protected abstract IQueryable<T> LoadDomain();
+        /// Should be overriden to load navigation properties of entity
+        protected virtual IQueryable<T> LoadDomain()
+        {
+            return reader.GetAll<T>();
+        }
     }
 }
diff --git a/SchengenVisaApi/Infrastructure/Database/Generic/IGenericReader.cs b/SchengenVisaApi/Infrastructure/Database/Generic/IGenericReader.cs
index ecdc94a..679f42c 100644
--- a/SchengenVisaApi/Infrastructure/Database/Generic/IGenericReader.cs
+++ b/SchengenVisaApi/Infrastructure/Database/Generic/IGenericReader.cs
@@ -2,9 +2,10 @@
 
 namespace Infrastructure.Database.Generic
 {
+    /// Reads from data storage
     public interface IGenericReader
     {
-        /// Get all entities of type <typeparamref name="T"/> stored in storage
+        /// Get all entities of type T stored in storage
         /// <typeparam name="T">Entity type to seek in storage</typeparam>
         IQueryable<T> GetAll<T>() where T : class, IEntity;
     }
diff --git a/SchengenVisaApi/Infrastructure/Database/Generic/IGenericRepository.cs b/SchengenVisaApi/Infrastructure/Database/Generic/IGenericRepository.cs
index e7ec271..5478600 100644
--- a/SchengenVisaApi/Infrastructure/Database/Generic/IGenericRepository.cs
+++ b/SchengenVisaApi/Infrastructure/Database/Generic/IGenericRepository.cs
@@ -2,18 +2,36 @@
 
 namespace Infrastructure.Database.Generic
 {
+    /// <summary>
+    /// Generic repository pattern
+    /// </summary>
+    /// <typeparam name="T">Entity type</typeparam>
     public interface IGenericRepository<T> where T : class, IEntity
     {
+        /// Get all entities from data storage
         Task<List<T>> GetAllAsync(CancellationToken cancellationToken);
 
+        /// Get one entity with specific id
+        /// <param name="id">Identifier of entity</param>
         Task<T> GetOneAsync(Guid id, CancellationToken cancellationToken);
 
+        /// Add entity to storage
+        /// <param name="entity">Entity to add</param>
         Task AddAsync(T entity, CancellationToken cancellationToken);
 
+        /// <summary>
+        /// Update entity in storage
+        /// </summary>
+        /// <param name="entity">Entity to update</param>
         Task UpdateAsync(T entity, CancellationToken cancellationToken);
 
+        /// <summary>
+        /// Remove entity from storage
+        /// </summary>
+        /// <param name="entity">Entity to remove</param>
         void Remove(T entity);
 
+        /// Save changes in storage
         Task SaveAsync(CancellationToken cancellationToken);
     }
 }
diff --git a/SchengenVisaApi/Infrastructure/Database/Generic/IGenericWriter.cs b/SchengenVisaApi/Infrastructure/Database/Generic/IGenericWriter.cs
index c53fefe..ab2b075 100644
--- a/SchengenVisaApi/Infrastructure/Database/Generic/IGenericWriter.cs
+++ b/SchengenVisaApi/Infrastructure/Database/Generic/IGenericWriter.cs
@@ -6,18 +6,18 @@ namespace Infrastructure.Database.Generic
     /// <remarks><see cref="IUnitOfWork"/> should be used to save changes</remarks>
     public interface IGenericWriter
     {
-        /// Add <paramref name="entity"/> to data storage
+        /// Add entity to data storage
         /// <param name="entity">Entity to add</param>
         /// <param name="cancellationToken">Cancellation Token</param>
         /// <typeparam name="T">Entity type</typeparam>
         Task AddAsync<T>(T entity, CancellationToken cancellationToken) where T : class, IEntity;
 
-        /// Update <paramref name="entity"/> in data storage
+        /// Update entity in data storage
         /// <param name="entity">Entity to update</param>
         /// <typeparam name="T">Entity type</typeparam>
         void Update<T>(T entity) where T : class, IEntity;
 
-        /// Remove <paramref name="entity"/> from data storage
+        /// Remove entity from data storage
         /// <param name="entity">Entity to remove</param>
         /// <typeparam name="T">Entity type</typeparam>
         void Remove<T>(T entity) where T : class, IEntity;
diff --git a/SchengenVisaApi/Infrastructure/Database/IUnitOfWork.cs b/SchengenVisaApi/Infrastructure/Database/IUnitOfWork.cs
index 2b068e8..653ddbc 100644
--- a/SchengenVisaApi/Infrastructure/Database/IUnitOfWork.cs
+++ b/SchengenVisaApi/Infrastructure/Database/IUnitOfWork.cs
@@ -2,7 +2,7 @@
 {
     public interface IUnitOfWork
     {
-        /// Save changes in data storage
+        /// Saves changes in data storage
         /// <param name="cancellationToken">Cancellation Token</param>
         Task SaveAsync(CancellationToken cancellationToken);
     }
diff --git a/SchengenVisaApi/Infrastructure/Database/Locations/Repositories/Cities/CitiesRepository.cs b/SchengenVisaApi/Infrastructure/Database/Locations/Repositories/Cities/CitiesRepository.cs
index da38369..b417188 100644
--- a/SchengenVisaApi/Infrastructure/Database/Locations/Repositories/Cities/CitiesRepository.cs
+++ b/SchengenVisaApi/Infrastructure/Database/Locations/Repositories/Cities/CitiesRepository.cs
@@ -4,12 +4,12 @@ using Microsoft.EntityFrameworkCore;
 
 namespace Infrastructure.Database.Locations.Repositories.Cities
 {
-    public class CitiesRepository(IGenericReader reader, IGenericWriter writer, IUnitOfWork unitOfWork)
-        : GenericRepository<City>(writer, unitOfWork), ICitiesRepository
+    public sealed class CitiesRepository(IGenericReader reader, IGenericWriter writer, IUnitOfWork unitOfWork)
+        : GenericRepository<City>(reader, writer, unitOfWork), ICitiesRepository
     {
         protected override IQueryable<City> LoadDomain()
         {
-            return reader.GetAll<City>().Include(c => c.Country);
+            return base.LoadDomain().Include(c => c.Country);
         }
     }
 }
diff --git a/SchengenVisaApi/Infrastructure/Database/Locations/Repositories/Countries/CountriesRepository.cs b/SchengenVisaApi/Infrastructure/Database/Locations/Repositories/Countries/CountriesRepository.cs
index f1ab02a..8d431b9 100644
--- a/SchengenVisaApi/Infrastructure/Database/Locations/Repositories/Countries/CountriesRepository.cs
+++ b/SchengenVisaApi/Infrastructure/Database/Locations/Repositories/Countries/CountriesRepository.cs
@@ -4,12 +4,12 @@ using Microsoft.EntityFrameworkCore;
 
 namespace Infrastructure.Database.Locations.Repositories.Countries
 {
-    public class CountriesRepository(IGenericReader reader, IGenericWriter writer, IUnitOfWork unitOfWork)
-        : GenericRepository<Country>(writer, unitOfWork), ICountriesRepository
+    public sealed class CountriesRepository(IGenericReader reader, IGenericWriter writer, IUnitOfWork unitOfWork)
+        : GenericRepository<Country>(reader, writer, unitOfWork), ICountriesRepository
     {
         protected override IQueryable<Country> LoadDomain()
         {
-            return reader.GetAll<Country>().Include(c => c.Cities);
+            return base.LoadDomain().Include(c => c.Cities);
         }
     }
 }
diff --git a/SchengenVisaApi/Infrastructure/Database/VisaApplications/Repositories/VisaApplicationsRepository.cs b/SchengenVisaApi/Infrastructure/Database/VisaApplications/Repositories/VisaApplicationsRepository.cs
index abbe608..d18d1f4 100644
--- a/SchengenVisaApi/Infrastructure/Database/VisaApplications/Repositories/VisaApplicationsRepository.cs
+++ b/SchengenVisaApi/Infrastructure/Database/VisaApplications/Repositories/VisaApplicationsRepository.cs
@@ -4,12 +4,12 @@ using Microsoft.EntityFrameworkCore;
 
 namespace Infrastructure.Database.VisaApplications.Repositories
 {
-    public class VisaApplicationsRepository(IGenericReader reader, IGenericWriter writer, IUnitOfWork unitOfWork)
-        : GenericRepository<VisaApplication>(writer, unitOfWork), IVisaApplicationsRepository
+    public sealed class VisaApplicationsRepository(IGenericReader reader, IGenericWriter writer, IUnitOfWork unitOfWork)
+        : GenericRepository<VisaApplication>(reader, writer, unitOfWork), IVisaApplicationsRepository
     {
         protected override IQueryable<VisaApplication> LoadDomain()
         {
-            return reader.GetAll<VisaApplication>()
+            return base.LoadDomain()
                 .Include(a => a.DestinationCountry)
                 .Include(a => a.PastVisas)
                 .Include(a => a.PastVisits);
diff --git a/SchengenVisaApi/Infrastructure/DependencyInjection.cs b/SchengenVisaApi/Infrastructure/DependencyInjection.cs
index 7b1ef0f..156abe4 100644
--- a/SchengenVisaApi/Infrastructure/DependencyInjection.cs
+++ b/SchengenVisaApi/Infrastructure/DependencyInjection.cs
@@ -10,8 +10,10 @@ using DbContext = Infrastructure.Database.DbContext;
 
 namespace Infrastructure
 {
+    /// Provides methods to add services to DI-container
     public static class DependencyInjection
     {
+        /// Add services needed for Infrastructure layer
         public static IServiceCollection AddInfrastructure(this IServiceCollection services)
         {
             //TODO строка подключения