diff --git a/search/archive.py b/search/archive.py
index 664cd7b..7b4631a 100644
--- a/search/archive.py
+++ b/search/archive.py
@@ -5,6 +5,8 @@ import analysis.archive ## circular...
 import analysis.query
 import analysis.format
 
+import threading
+
 class Archive():
 
 	def __init__(self, archives_dir=None):
@@ -16,6 +18,9 @@ class Archive():
 
 		self.loaded = False
 
+		self.lock_search = threading.Lock()
+		self.lock_threads_ranking = threading.Lock()
+
 	def load(self, archive_name=None):
 
 		if archive_name == None:
@@ -59,46 +64,50 @@ class Archive():
 
 	def search(self, keyword, field='content', min_hits=0):
 
-		search_results = { "keyword": keyword, "field": field, "archive": self.archive_name, "results": [] }
+		with self.lock_search:
 
-		for k, v in sorted(self.archive.items(), key=get_key, reverse=True):
+			search_results = { "keyword": keyword, "field": field, "archive": self.archive_name, "results": [] }
 
-			current_index_str = self.archive_name + '/' + k
-			hits = []
-			nbr_hits = 0
-			i = 0
-			for m in v['threads']:
-				current_index_str = self.archive_name + '/' + k + '/' + str(i)
-				nbr_hits += self.search_message(keyword, m, current_index_str, hits, field)
-				i += 1
+			for k, v in sorted(self.archive.items(), key=get_key, reverse=True):
 
-			if nbr_hits > min_hits:
-				# nettime-l - fix (the name of the thread from ex. 'nettime-l_Jan_01' to 'January 2001')
-				if k.startswith("nettime-l_"):
-					dt = datetime.strptime(k, "nettime-l_%b_%y")
-					k = dt.strftime("%B_%Y")
-				search_results['results'].append({ 'thread': k, 'nbr_hits': nbr_hits, 'hits': hits})
+				current_index_str = self.archive_name + '/' + k
+				hits = []
+				nbr_hits = 0
+				i = 0
+				for m in v['threads']:
+					current_index_str = self.archive_name + '/' + k + '/' + str(i)
+					nbr_hits += self.search_message(keyword, m, current_index_str, hits, field)
+					i += 1
 
-		return search_results
+				if nbr_hits > min_hits:
+					# nettime-l - fix (the name of the thread from ex. 'nettime-l_Jan_01' to 'January 2001')
+					if k.startswith("nettime-l_"):
+						dt = datetime.strptime(k, "nettime-l_%b_%y")
+						k = dt.strftime("%B_%Y")
+					search_results['results'].append({ 'thread': k, 'nbr_hits': nbr_hits, 'hits': hits})
+
+			return search_results
 
 	def threads_ranking(self, rank=5):
 
-		search_results = { "keyword": "thread ranking", "field": "ranking", "archive": self.archive_name, "results": [] }
+		with self.lock_threads_ranking:
 
-		a = analysis.archive.Archive(self)
-		q = a.query();
+			search_results = { "keyword": "thread ranking", "field": "ranking", "archive": self.archive_name, "results": [] }
 
-		ranking = q.threads_ranking(rank=rank)
+			a = analysis.archive.Archive(self)
+			q = a.query();
 
-		for i in ranking:
-			r = analysis.format.frame_to_dictionary_threads_ranking(ranking[i])
-			for h in r:
-				hit = [{ 'url': h['url'], 'subject': h['subject'], 'author_name': h['from']}]				
-				search_results['results'].append({'thread': h['date'], 'nbr_hits': h['nbr-references'], 'hits': hit})
-		del a
-		del q
+			ranking = q.threads_ranking(rank=rank)
 
-		return search_results
+			for i in ranking:
+				r = analysis.format.frame_to_dictionary_threads_ranking(ranking[i])
+				for h in r:
+					hit = [{ 'url': h['url'], 'subject': h['subject'], 'author_name': h['from']}]				
+					search_results['results'].append({'thread': h['date'], 'nbr_hits': h['nbr-references'], 'hits': hit})
+			del a
+			del q
+
+			return search_results