diff --git a/parsing.py b/parsing.py
index 52b028e..1b66383 100644
--- a/parsing.py
+++ b/parsing.py
@@ -20,44 +20,44 @@
 # USI specification: http://www.psidev.info/usi
 usi_pattern = re.compile(
     # mzspec preamble
-    '^mzspec'
+    r'^mzspec'
     # collection identifier
     # Proteomics collection identifiers: PXDnnnnnn, MSVnnnnnnnnn, RPXDnnnnnn,
     #                                    PXLnnnnnn
     # Unofficial: MASSIVEKB
     # https://github.com/HUPO-PSI/usi/blob/master/CollectionIdentifiers.md
-    ':(MSV\d{9}|PXD\d{6}|PXL\d{6}|RPXD\d{6})'
+    r':(MSV\d{9}|PXD\d{6}|PXL\d{6}|RPXD\d{6})'
     # msRun identifier
-    ':(.*)'
+    r':(.*)'
     # index flag
-    ':(scan|index|nativeId|trace)'
+    r':(scan|index|nativeId|trace)'
     # index number
-    ':(.+)'
+    r':(.+)'
     # optional spectrum interpretation
-    '(:.+)?$',
+    r'(:.+)?$',
     flags=re.IGNORECASE
 )
 # OR: Metabolomics USIs.
 usi_pattern_draft = re.compile(
     # mzdraft preamble
-    '^(?:mzspec|mzdraft)'
+    r'^(?:mzspec|mzdraft)'
     # collection identifier
     # Unofficial proteomics spectral library identifier: MASSIVEKB
     # Metabolomics collection identifiers: GNPS, MASSBANK, MS2LDA, MOTIFDB
-    ':(MASSIVEKB|GNPS|MASSBANK|MS2LDA|MOTIFDB)'
+    r':(MASSIVEKB|GNPS|MASSBANK|MS2LDA|MOTIFDB)'
     # msRun identifier
-    ':(.*)'
+    r':(.*)'
     # index flag
-    ':(scan|index|nativeId|trace|accession)'
+    r':(scan|index|nativeId|trace|accession)'
     # index number
-    ':(.+)'
+    r':(.+)'
     # optional spectrum interpretation
-    '(:.+)?$',
+    r'(:.+)?$',
     flags=re.IGNORECASE
 )
-gnps_task_pattern = re.compile('^TASK-([a-z0-9]{32})-(.+)$',
+gnps_task_pattern = re.compile(r'^TASK-([a-z0-9]{32})-(.+)$',
                                flags=re.IGNORECASE)
-ms2lda_task_pattern = re.compile('^TASK-(\d+)$', flags=re.IGNORECASE)
+ms2lda_task_pattern = re.compile(r'^TASK-(\d+)$', flags=re.IGNORECASE)
 
 splash_builder = splash.Splash()
 
diff --git a/run_server.sh b/run_server.sh
index 92e62f1..141426d 100755
--- a/run_server.sh
+++ b/run_server.sh
@@ -1,4 +1,4 @@
 #!/bin/bash
 source activate usi
 
-gunicorn -w 2 -b 0.0.0.0:5000 --timeout 3600 main:app --access-logfile /app/logs/access.log --max-requests 1000
+gunicorn -w 2 --threads=1 -b 0.0.0.0:5000 main:app --access-logfile /app/logs/access.log --timeout 30 --max-requests 100 --max-requests-jitter 20
\ No newline at end of file
diff --git a/templates/mirror.html b/templates/mirror.html
index 9d12e73..e499e10 100644
--- a/templates/mirror.html
+++ b/templates/mirror.html
@@ -69,6 +69,13 @@
             </div>
             <div class="row mt-2">
                 <div class="col-2 offset-4">
+                    <a class="btn btn-primary"
+                       id="download_json"
+                       href="/json/mirror/?usi1=(( usi1 ))&usi2=(( usi2 ))">
+                        Download as JSON
+                    </a>
+                </div>
+                <div class="col-2">
                     <a class="btn btn-primary"
                        id="download_svg"
                        href="/svg/mirror/?usi1=(( usi1 ))&usi2=(( usi2 ))"
diff --git a/test/locustfile.py b/test/locustfile.py
index eca50d5..f984f7b 100644
--- a/test/locustfile.py
+++ b/test/locustfile.py
@@ -73,3 +73,10 @@ def generate_mirror_svg(self):
         usi2 = random.choice(usis_to_test)
         self.client.get(f'/svg/mirror/?usi1={usi1}&usi2={usi2}',
                         name='/svg/mirror/')
+
+    @locust.task
+    def generate_mirror_json(self):
+        usi1 = random.choice(usis_to_test)
+        usi2 = random.choice(usis_to_test)
+        self.client.get(f'/json/mirror/?usi1={usi1}&usi2={usi2}',
+                        name='/json/mirror/')
diff --git a/test/test_integration.py b/test/test_integration.py
index 3538de8..81938ea 100644
--- a/test/test_integration.py
+++ b/test/test_integration.py
@@ -35,6 +35,8 @@ def _get_splash_remote(spectrum):
     splash_response = requests.post(
         'https://splash.fiehnlab.ucdavis.edu/splash/it',
         data=json.dumps(payload), headers=headers)
+    if splash_response.status_code != 200:
+        pytest.skip('external SPLASH unavailable')
     return splash_response.text
 
 
@@ -473,6 +475,28 @@ def test_peak_csv_invalid(client):
             assert response.status_code == status_code, usi
 
 
+def test_mirror_json(client):
+    for usi1, usi2 in pairwise(usis_to_test):
+        response = client.get('/json/mirror/',
+                              query_string=f'usi1={usi1}&usi2={usi2}')
+        assert response.status_code == 200
+        response_dict = json.loads(response.data)
+        assert 'spectrum1' in response_dict
+        assert 'spectrum2' in response_dict
+        assert 'cosine' in response_dict
+        assert 'n_peak_matches' in response_dict
+        assert 'peak_matches' in response_dict
+        assert (response_dict['n_peak_matches']
+                == len(response_dict['peak_matches']))
+        for peak_match in response_dict['peak_matches']:
+            assert len(peak_match) == 2
+        for i, usi in enumerate((usi1, usi2), 1):
+            mz, intensity = zip(*response_dict[f'spectrum{i}']['peaks'])
+            assert (response_dict[f'spectrum{i}']['splash']
+                    == _get_splash_remote(sus.MsmsSpectrum(usi, 0, 0, mz,
+                                                           intensity)))
+
+
 def test_generate_qr(client):
     for usi in usis_to_test:
         response = client.get('/qrcode/', query_string=f'usi={usi}')
diff --git a/test/test_unit.py b/test/test_unit.py
index 0f08c95..f370411 100644
--- a/test/test_unit.py
+++ b/test/test_unit.py
@@ -32,6 +32,8 @@ def _get_splash_remote(spectrum):
     splash_response = requests.post(
         'https://splash.fiehnlab.ucdavis.edu/splash/it',
         data=json.dumps(payload), headers=headers)
+    if splash_response.status_code != 200:
+        pytest.skip('external SPLASH unavailable')
     return splash_response.text
 
 
diff --git a/test/usi_test_data.py b/test/usi_test_data.py
index f254d06..25dec10 100644
--- a/test/usi_test_data.py
+++ b/test/usi_test_data.py
@@ -6,6 +6,7 @@
     # FIXME: RPXD not resolved by MassIVE.
     # 'mzspec:RPXD006668:Adult_Frontalcortex_bRP_Elite_85_f09:scan:17555',
     'mzspec:GNPS:TASK-c95481f0c53d42e78a61bf899e9f9adb-spectra/specs_ms.mgf:scan:1943',
+    'mzspec:GNPS:TASK-9c27c9cc037c443dbecafb07039a8528-spectra/specs_ms.mgf:scan:1',
     'mzspec:GNPS:GNPS-LIBRARY:accession:CCMSLIB00005436077',
     'mzspec:MASSBANK::accession:SM858102',
     'mzspec:MS2LDA:TASK-190:accession:270684',
diff --git a/views.py b/views.py
index 7474e21..b320fde 100644
--- a/views.py
+++ b/views.py
@@ -715,6 +715,46 @@ def peak_json():
     return flask.jsonify(result_dict)
 
 
+@blueprint.route('/json/mirror/')
+def mirror_json():
+    try:
+        usi1 = flask.request.args.get('usi1')
+        usi2 = flask.request.args.get('usi2')
+
+        plotting_args = _get_plotting_args(flask.request.args, mirror=True)
+        spectrum1, source1, splash_key1 = parsing.parse_usi(usi1)
+        spectrum2, source2, splash_key2 = parsing.parse_usi(usi2)
+        _spectrum1, _spectrum2 = _prepare_mirror_spectra(spectrum1, spectrum2,
+                                                         plotting_args)
+        similarity, peak_matches = _cosine(
+            _spectrum1, _spectrum2, plotting_args['fragment_mz_tolerance'],
+            plotting_args['cosine'] == 'shifted')
+
+        spectrum1_dict = {
+            'peaks': _get_peaks(spectrum1),
+            'n_peaks': len(spectrum1.mz),
+            'precursor_mz': spectrum1.precursor_mz,
+            'splash': splash_key1
+        }
+        spectrum2_dict = {
+            'peaks': _get_peaks(spectrum2),
+            'n_peaks': len(spectrum2.mz),
+            'precursor_mz': spectrum2.precursor_mz,
+            'splash': splash_key2
+        }
+        result_dict = {'spectrum1': spectrum1_dict,
+                       'spectrum2': spectrum2_dict,
+                       'cosine': similarity,
+                       'n_peak_matches': len(peak_matches),
+                       'peak_matches': peak_matches}
+
+    except UsiError as e:
+        result_dict = {'error': {'code': e.error_code, 'message': str(e)}}
+    except ValueError as e:
+        result_dict = {'error': {'code': 404, 'message': str(e)}}
+    return flask.jsonify(result_dict)
+
+
 @blueprint.route('/proxi/v0.1/spectra')
 def peak_proxi_json():
     try: