Code review

AuthConfig.cs

app.UseCookieAuthentication(new CookieAuthenticationOptions
            {
                AuthenticationType = DefaultAuthenticationTypes.ApplicationCookie,
                ExpireTimeSpan = TimeSpan.FromDays(30),
                SlidingExpiration = true,
                Provider = new CookieAuthenticationProvider
                {
                    OnValidateIdentity = async cookieCtx =>
                    {
                        var validator = DependencyResolver.Current.GetService<IAuthenticationSessionValidator>();
                        var isValid = false;
                        if (cookieCtx.Properties.IssuedUtc.HasValue)
                        {
                            cookieCtx.Identity.AddClaim(new Claim(Constants.ClaimTypes.AuthenticationTime,
                                cookieCtx.Properties.IssuedUtc.Value.ToEpochTime().ToString()));
                            isValid =
                                await
                                    validator.IsAuthenticationSessionValidAsync(new ClaimsPrincipal(cookieCtx.Identity));
                        }
                        if (isValid == false)
                        {
                            cookieCtx.RejectIdentity();
                        }
                    }
                }
            });

SessionValidator.cs

public class DataEntryAuthenticationSessionValidator : IAuthenticationAppSessionValidator
    {
        private readonly IMediator _mediator;

        public DataEntryAuthenticationSessionValidator(IMediator mediator)
        {
            _mediator = mediator;
        }

        public Task<bool> IsAuthenticationSessionValidAsync(CookieValidateIdentityContext ctx)
        {
            var date = _mediator.Send(new ReadRecordQuery<PractitionerRecord>(ctx.Identity.GetSubjectId())).Updated;
            return
                Task.FromResult(ctx.Properties.IssuedUtc.HasValue &&
                                DateTimeOffset.Compare(new DateTimeOffset(date), ctx.Properties.IssuedUtc.Value) < 0);
        }
    }