diff --git a/lib/OpenQA/WebSockets.pm b/lib/OpenQA/WebSockets.pm
index b00e3363ee6..38d83c2df1a 100644
--- a/lib/OpenQA/WebSockets.pm
+++ b/lib/OpenQA/WebSockets.pm
@@ -19,6 +19,9 @@ sub startup {
     $self->_setup if $RUNNING;
 
     $self->defaults(appname => 'openQA Websocket Server');
+    if (defined(my $max_online_workers = $self->config->{misc_limits}->{max_online_workers})) {
+        $self->log->info("Limiting number of online worker slots to $max_online_workers");
+    }
 
     # no cookies for worker, no secrets to protect
     $self->secrets(['nosecretshere']);
diff --git a/t/27-websockets.t b/t/27-websockets.t
index a336ee9c108..220dba131d5 100644
--- a/t/27-websockets.t
+++ b/t/27-websockets.t
@@ -35,9 +35,10 @@ my $jobs = $schema->resultset('Jobs');
 my $worker = $workers->find({host => 'localhost', instance => 1});
 my $worker_id = $worker->id;
 my $status = OpenQA::WebSockets::Model::Status->singleton->workers;
+my $app = $t->app;
+my $worker_by_txn = $app->status->worker_by_transaction;
 
 subtest 'Authentication' => sub {
-    my $app = $t->app;
 
     combined_like {
         $t->get_ok('/test')->status_is(404)->content_like(qr/Not found/);
@@ -76,6 +77,7 @@ subtest 'API' => sub {
     $t->status_is(429, 'no ws connection for limited worker')->content_like(qr/Limit.*exceeded/, 'error about limit');
     $worker->discard_changes;
     like $worker->error, qr/^limited at .*/, 'worker flagged as limited via error field excluding it from assignments';
+    is keys %$worker_by_txn, 0, 'no transaction added for limited worker';
 };
 
 $misc_limits->{max_online_workers} = undef;
@@ -120,8 +122,10 @@ subtest 'web socket message handling' => sub {
     subtest 'accepted' => sub {
         combined_like {
             $t->websocket_ok('/ws/1', 'establish ws connection');
+            is keys %$worker_by_txn, 1, 'transaction added for online worker';
             $t->send_ok('{"type":"accepted","jobid":42}');
             $t->finish_ok(1000, 'finished ws connection');
+            is keys %$worker_by_txn, 0, 'transaction removed if worker no longer online';
         }
         qr/Worker 1 accepted job 42.*never assigned/s, 'warning logged when job has never been assigned';
 
@@ -139,9 +143,12 @@ subtest 'web socket message handling' => sub {
     subtest 'multiple ws connections handled gracefully' => sub {
         combined_like {
             $t->websocket_ok('/ws/1', 'establish first ws connection');
+            is keys %$worker_by_txn, 1, 'transaction added for online worker';
             $t2->websocket_ok('/ws/1', 'establish second ws connection');
             $t->finished_ok(1008, 'first ws connection finished due to second connection');
+            is keys %$worker_by_txn, 1, 'first transaction removed, so still only one txn';
             $t2->finish_ok(1000, 'finished second ws connection');
+            is keys %$worker_by_txn, 0, 'all transactions removed';
         }
         qr/only one connection per worker allowed/s, '2nd connection attempt logged';
     };
diff --git a/t/43-scheduling-and-worker-scalability.t b/t/43-scheduling-and-worker-scalability.t
index 03273fedb34..07ad6ffade5 100644
--- a/t/43-scheduling-and-worker-scalability.t
+++ b/t/43-scheduling-and-worker-scalability.t
@@ -4,11 +4,13 @@
 
 use Test::Most;
 
+use Mojo::Base -signatures;
 use Test::Warnings ':report_warnings';
 use Test::MockModule;
 use Time::HiRes 'sleep';
 use File::Path 'make_path';
 use Scalar::Util 'looks_like_number';
+use List::Util qw(min max);
 use Mojo::File qw(path tempfile);
 use Mojo::Util 'dumper';
 use IPC::Run qw(start);
@@ -39,7 +41,7 @@ BEGIN {
 }
 
 setup_mojo_app_with_default_worker_timeout;
-OpenQA::Setup::read_config(OpenQA::App->singleton);
+OpenQA::Setup::read_config(my $app = OpenQA::App->singleton);
 
 my $load_avg_file = simulate_load('0.93 0.95 3.25 2/2207 1212', '43-scheduling-and-worker-scalability');
 
@@ -58,6 +60,18 @@ my $schema = OpenQA::Test::Database->new->create;
 my $workers = $schema->resultset('Workers');
 my $jobs = $schema->resultset('Jobs');
 
+# configure websocket server to apply SCALABILITY_TEST_WORKER_LIMIT
+my $worker_limit = $ENV{SCALABILITY_TEST_WORKER_LIMIT} // 100;
+my $web_socket_server_mock = Test::MockModule->new('OpenQA::WebSockets');
+my $configure_web_socket_server = sub ($self, @args) {
+    my $original_function = $web_socket_server_mock->original('_setup');
+    my $original_return_value = $original_function->($self, @args);
+    $self->config->{misc_limits}->{max_online_workers} = $worker_limit;
+    return $original_return_value;
+};
+$web_socket_server_mock->redefine(_setup => $configure_web_socket_server);
+$configure_web_socket_server->($app);    # invoke this function here for the sake of tracking coverage
+
 # create web UI and websocket server
 my $web_socket_server = create_websocket_server(undef, 0, 1, 1);
 my $webui = create_webapi(undef, 1);
@@ -130,20 +144,36 @@ my $polling_tries_workers = $seconds_to_wait_per_worker / $polling_interval * $w
 my $polling_tries_jobs = $seconds_to_wait_per_job / $polling_interval * $job_count;
 
 subtest 'wait for workers to be idle' => sub {
+    # wait for all workers to register
     my @worker_search_args = ({'properties.key' => 'WEBSOCKET_API_VERSION'}, {join => 'properties'});
+    my $actual_count = 0;
     for my $try (1 .. $polling_tries_workers) {
-        last if $workers->search(@worker_search_args)->count == $worker_count;
-        note("Waiting until all workers are registered, try $try");
-        sleep $polling_interval;
+        last if ($actual_count = $workers->search(@worker_search_args)->count) == $worker_count;
+        note("Waiting until all workers are registered, try $try");    # uncoverable statement
+        sleep $polling_interval;    # uncoverable statement
     }
-    is($workers->count, $worker_count, 'all workers registered');
+    is $actual_count, $worker_count, 'all workers registered';
+
+    # wait for expected number of workers to become limited
+    my $limited_workers = max(0, $worker_count - $worker_limit);
+    $worker_count = min($worker_count, $worker_limit);
+    for my $try (1 .. $polling_tries_workers) {
+        last if ($actual_count = $workers->search({error => {-like => '%limited%'}})->count) == $limited_workers;
+        note("Waiting until $limited_workers workers are limited, try $try");    # uncoverable statement
+        sleep $polling_interval;    # uncoverable statement
+    }
+    is $actual_count, $limited_workers, 'expected number of workers limited';
+
+    # check that no workers are in unexpected offline/error states
     my @non_idle_workers;
     for my $worker ($workers->all) {
-        $worker_ids{$worker->id} = 1;
-        push(@non_idle_workers, $worker->info)
-          if $worker->status ne 'idle' || ($worker->websocket_api_version || 0) != WEBSOCKET_API_VERSION;
+        my $is_idle = $worker->status eq 'idle';
+        my $is_idle_or_limited = $is_idle || $worker->error =~ qr/limited/;
+        $worker_ids{$worker->id} = 1 if $is_idle;
+        push(@non_idle_workers, $worker->info)    # uncoverable statement
+          if !$is_idle_or_limited || ($worker->websocket_api_version || 0) != WEBSOCKET_API_VERSION;
     }
-    ok(!@non_idle_workers, 'all workers idling') or diag explain \@non_idle_workers;
+    is scalar @non_idle_workers, 0, 'all workers idling/limited' or diag explain \@non_idle_workers;
 };
 
 subtest 'assign and run jobs' => sub {
@@ -166,7 +196,7 @@ subtest 'assign and run jobs' => sub {
         is(scalar @$allocated, $job_count, 'each job has a worker assigned');
     }
     else {
-        # uncoverable statement only executed when the number of workers is # jobs are equal based on config parameters
+        # uncoverable statement only executed when the number of workers and jobs are equal based on config parameters
         is(scalar @$allocated, $job_count, 'all jobs assigned and all workers busy');
         # uncoverable statement count:1
         # uncoverable statement count:2
@@ -187,7 +217,7 @@ subtest 'assign and run jobs' => sub {
     }
     for my $try (1 .. $polling_tries_jobs) {
         last if $jobs->search({state => DONE})->count == $job_count;
-        if ($jobs->search({state => SCHEDULED})->count > $remaining_jobs) {
+        if ($jobs->search({state => SCHEDULED})->count > max(0, $remaining_jobs)) {
             # uncoverable statement
             note('At least one job has been set back to scheduled; aborting to wait until all jobs are done');
             last;    # uncoverable statement