diff --git a/cara/apps/calculator/__init__.py b/cara/apps/calculator/__init__.py
index f5f2a383..15572267 100644
--- a/cara/apps/calculator/__init__.py
+++ b/cara/apps/calculator/__init__.py
@@ -5,6 +5,7 @@ import asyncio
 import concurrent.futures
 import datetime
 import base64
+import functools
 import html
 import json
 import os
@@ -15,7 +16,9 @@ import uuid
 import zlib
 
 import jinja2
+import loky
 from tornado.web import Application, RequestHandler, StaticFileHandler
+import tornado.log
 
 from . import markdown_tools
 from . import model_generator
@@ -111,10 +114,18 @@ class ConcentrationModel(BaseRequestHandler):
 
         base_url = self.request.protocol + "://" + self.request.host
         report_generator: ReportGenerator = self.settings['report_generator']
-        report = report_generator.build_report(base_url, form)
-        if self.settings.get("debug", False):
-            dt = (datetime.datetime.now() - start)
-            print(f'Report response time {dt.seconds}.{dt.microseconds}s')
+        executor = loky.get_reusable_executor(
+            max_workers=self.settings['handler_worker_pool_size'],
+            timeout=300,
+        )
+        report_task = executor.submit(
+            report_generator.build_report, base_url, form,
+            executor_factory=functools.partial(
+                concurrent.futures.ThreadPoolExecutor,
+                self.settings['report_generation_parallelism'],
+            ),
+        )
+        report: str = await asyncio.wrap_future(report_task)
         self.finish(report)
 
 
@@ -123,11 +134,18 @@ class StaticModel(BaseRequestHandler):
         form = model_generator.FormData.from_dict(model_generator.baseline_raw_form_data())
         base_url = self.request.protocol + "://" + self.request.host
         report_generator: ReportGenerator = self.settings['report_generator']
-        report = report_generator.build_report(base_url, form)
+        executor = loky.get_reusable_executor(max_workers=self.settings['handler_worker_pool_size'])
+        report_task = executor.submit(
+            report_generator.build_report, base_url, form,
+            executor_factory=functools.partial(
+                concurrent.futures.ThreadPoolExecutor,
+                self.settings['report_generation_parallelism'],
+            ),
+        )
+        report: str = await asyncio.wrap_future(report_task)
         self.finish(report)
 
 
-
 class LandingPage(BaseRequestHandler):
     def get(self):
         template = self.settings["template_environment"].get_template(
@@ -222,6 +240,9 @@ def make_app(
         template_environment.get_template('common_text.md.j2')
     )
 
+    if debug:
+        tornado.log.enable_pretty_logging()
+
     return Application(
         urls,
         debug=debug,
@@ -233,4 +254,19 @@ def make_app(
         # COOKIE_SECRET being undefined will result in no login information being
         # presented to the user.
         cookie_secret=os.environ.get('COOKIE_SECRET', '<undefined>'),
+
+        # Process parallelism controls. There is a balance between serving a single report
+        # requests quickly or serving multiple requests concurrently.
+        # The defaults are: handle one report at a time, and allow parallelism
+        # of that report generation. A value of ``None`` will result in the number of
+        # processes being determined based on the number of CPUs. For some deployments,
+        # such as on OpenShift this number does *not* reflect the real number of CPUs that
+        # can be used, and it is recommended to specify these values explicitly (through
+        # the environment variables).
+        handler_worker_pool_size=(
+            int(os.environ.get("HANDLER_WORKER_POOL_SIZE", 1)) or None
+        ),
+        report_generation_parallelism=(
+            int(os.environ.get('REPORT_PARALLELISM', 0)) or None
+        ),
     )
diff --git a/cara/apps/calculator/report_generator.py b/cara/apps/calculator/report_generator.py
index 9304ffe5..e12b7c98 100644
--- a/cara/apps/calculator/report_generator.py
+++ b/cara/apps/calculator/report_generator.py
@@ -4,15 +4,16 @@ import dataclasses
 from datetime import datetime, timedelta
 import io
 import typing
+import urllib
 import zlib
 
-import qrcode
-import urllib
+import loky
 import jinja2
 import matplotlib
 matplotlib.use('agg')
 import matplotlib.pyplot as plt
 import numpy as np
+import qrcode
 
 from cara import models
 from ... import monte_carlo as mc
@@ -251,15 +252,20 @@ def scenario_statistics(mc_model: mc.ExposureModel, sample_times: np.ndarray):
     }
 
 
-def comparison_report(scenarios: typing.Dict[str, mc.ExposureModel], sample_times: np.ndarray):
+def comparison_report(
+        scenarios: typing.Dict[str, mc.ExposureModel],
+        sample_times: np.ndarray,
+        executor_factory: typing.Callable[[], concurrent.futures.Executor],
+):
     statistics = {}
-    with concurrent.futures.ProcessPoolExecutor() as executor:
+    with executor_factory() as executor:
         results = executor.map(
             scenario_statistics,
             scenarios.values(),
             [sample_times] * len(scenarios),
             timeout=60,
         )
+
     for (name, model), model_stats in zip(scenarios.items(), results):
         statistics[name] = model_stats
     return {
@@ -273,12 +279,23 @@ class ReportGenerator:
     jinja_loader: jinja2.BaseLoader
     calculator_prefix: str
 
-    def build_report(self, base_url: str, form: FormData) -> str:
+    def build_report(
+            self,
+            base_url: str,
+            form: FormData,
+            executor_factory: typing.Callable[[], concurrent.futures.Executor],
+    ) -> str:
         model = form.build_model()
-        context = self.prepare_context(base_url, model, form)
+        context = self.prepare_context(base_url, model, form, executor_factory=executor_factory)
         return self.render(context)
 
-    def prepare_context(self, base_url: str, model: models.ExposureModel, form: FormData) -> dict:
+    def prepare_context(
+            self,
+            base_url: str,
+            model: models.ExposureModel,
+            form: FormData,
+            executor_factory: typing.Callable[[], concurrent.futures.Executor],
+    ) -> dict:
         now = datetime.utcnow().astimezone()
         time = now.strftime("%Y-%m-%d %H:%M:%S UTC")
 
@@ -293,7 +310,9 @@ class ReportGenerator:
 
         context.update(calculate_report_data(model))
         alternative_scenarios = manufacture_alternative_scenarios(form)
-        context['alternative_scenarios'] = comparison_report(alternative_scenarios, scenario_sample_times)
+        context['alternative_scenarios'] = comparison_report(
+            alternative_scenarios, scenario_sample_times, executor_factory=executor_factory,
+        )
         context['qr_code'] = generate_qr_code(base_url, self.calculator_prefix, form)
         context['calculator_prefix'] = self.calculator_prefix
         context['scale_warning'] = {
diff --git a/cara/tests/apps/calculator/test_report_generator.py b/cara/tests/apps/calculator/test_report_generator.py
index 75733d5f..91c6a02c 100644
--- a/cara/tests/apps/calculator/test_report_generator.py
+++ b/cara/tests/apps/calculator/test_report_generator.py
@@ -1,8 +1,10 @@
+import concurrent.futures
+from functools import partial
 import time
 
 import pytest
 
-from cara.apps.calculator import report_generator
+from cara.apps.calculator.report_generator import ReportGenerator, readable_minutes
 from cara.apps.calculator import make_app
 
 
@@ -15,8 +17,10 @@ def test_generate_report(baseline_form):
 
     start = time.perf_counter()
 
-    generator: report_generator.ReportGenerator = make_app().settings['report_generator']
-    report = generator.build_report("", baseline_form)
+    generator: ReportGenerator = make_app().settings['report_generator']
+    report = generator.build_report("", baseline_form, partial(
+        concurrent.futures.ThreadPoolExecutor, 1,
+    ))
     end = time.perf_counter()
     assert report != ""
     assert end - start < time_limit
@@ -33,4 +37,4 @@ def test_generate_report(baseline_form):
     ],
 )
 def test_readable_minutes(test_input, expected):
-    assert report_generator.readable_minutes(test_input) == expected
+    assert readable_minutes(test_input) == expected
diff --git a/cara/tests/apps/calculator/test_webapp.py b/cara/tests/apps/calculator/test_webapp.py
index edbbe9f4..40b75595 100644
--- a/cara/tests/apps/calculator/test_webapp.py
+++ b/cara/tests/apps/calculator/test_webapp.py
@@ -63,9 +63,7 @@ class TestBasicApp(tornado.testing.AsyncHTTPTestCase):
         # but the end time is after the other request (because it takes longer
         # to process a report than a simple page).
         assert response.start_time < other_response.start_time
-        # Known fail after reverting in https://gitlab.cern.ch/cara/cara/-/merge_requests/219.
-        with pytest.raises(AssertionError):
-            assert end_time(response) > end_time(other_response)
+        assert end_time(response) > end_time(other_response)
 
         self.assertEqual(response.code, 200)
         assert 'CERN HSE' not in response.body.decode()
diff --git a/requirements.txt b/requirements.txt
index eac04f3e..c036b924 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -35,6 +35,7 @@ jupyter-server==1.4.1
 jupyterlab-pygments==0.1.2
 jupyterlab-widgets==1.0.0
 kiwisolver==1.3.1
+loky==2.9.0
 MarkupSafe==1.1.1
 matplotlib==3.3.4
 memoization==0.3.2
@@ -53,6 +54,7 @@ pickleshare==0.7.5
 Pillow==8.1.0
 prometheus-client==0.9.0
 prompt-toolkit==3.0.16
+psutil==5.8.0
 ptyprocess==0.7.0
 pycparser==2.20
 Pygments==2.8.0
diff --git a/setup.cfg b/setup.cfg
index f40978b4..21bbf8d4 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -5,7 +5,7 @@ addopts = --mypy
 [mypy]
 no_warn_no_return = True
 
-[mypy-matplotlib.*]
+[mypy-loky.*]
 ignore_missing_imports = True
 
 [mypy-ipympl.*]
@@ -14,6 +14,9 @@ ignore_missing_imports = True
 [mypy-ipywidgets.*]
 ignore_missing_imports = True
 
+[mypy-matplotlib.*]
+ignore_missing_imports = True
+
 [mypy-mistune.*]
 ignore_missing_imports = True
 
diff --git a/setup.py b/setup.py
index 5fa01807..8a4a9c86 100644
--- a/setup.py
+++ b/setup.py
@@ -23,10 +23,12 @@ REQUIREMENTS: dict = {
         'ipympl',
         'ipywidgets',
         'Jinja2',
+        'loky',
         'matplotlib',
         'memoization',
         'mistune',
         'numpy',
+        'psutil',
         'qrcode[pil]',
         'scipy',
         'sklearn',