diff --git a/module/Core/src/Domain/Repository/DomainRepository.php b/module/Core/src/Domain/Repository/DomainRepository.php
index 2e4f3bb2..99a7a927 100644
--- a/module/Core/src/Domain/Repository/DomainRepository.php
+++ b/module/Core/src/Domain/Repository/DomainRepository.php
@@ -4,6 +4,7 @@ declare(strict_types=1);
 
 namespace Shlinkio\Shlink\Core\Domain\Repository;
 
+use Doctrine\DBAL\LockMode;
 use Doctrine\ORM\Query\Expr\Join;
 use Happyr\DoctrineSpecification\Repository\EntitySpecificationRepository;
 use Shlinkio\Shlink\Core\Entity\Domain;
@@ -32,4 +33,16 @@ class DomainRepository extends EntitySpecificationRepository implements DomainRe
 
         return $qb->getQuery()->getResult();
     }
+
+    public function findOneByAuthorityWithLock(string $authority): ?Domain
+    {
+        $qb = $this->createQueryBuilder('d');
+        $qb->where($qb->expr()->eq('d.authority', ':authority'))
+           ->setParameter('authority', $authority)
+           ->setMaxResults(1);
+
+        $query = $qb->getQuery()->setLockMode(LockMode::PESSIMISTIC_WRITE);
+
+        return $query->getOneOrNullResult();
+    }
 }
diff --git a/module/Core/src/Domain/Repository/DomainRepositoryInterface.php b/module/Core/src/Domain/Repository/DomainRepositoryInterface.php
index 1d201520..5dc2f873 100644
--- a/module/Core/src/Domain/Repository/DomainRepositoryInterface.php
+++ b/module/Core/src/Domain/Repository/DomainRepositoryInterface.php
@@ -15,4 +15,6 @@ interface DomainRepositoryInterface extends ObjectRepository, EntitySpecificatio
      * @return Domain[]
      */
     public function findDomainsWithout(?string $excludedAuthority, ?ApiKey $apiKey = null): array;
+
+    public function findOneByAuthorityWithLock(string $authority): ?Domain;
 }
diff --git a/module/Core/src/Repository/TagRepository.php b/module/Core/src/Repository/TagRepository.php
index d21122d0..38aae1dc 100644
--- a/module/Core/src/Repository/TagRepository.php
+++ b/module/Core/src/Repository/TagRepository.php
@@ -4,6 +4,7 @@ declare(strict_types=1);
 
 namespace Shlinkio\Shlink\Core\Repository;
 
+use Doctrine\DBAL\LockMode;
 use Happyr\DoctrineSpecification\Repository\EntitySpecificationRepository;
 use Happyr\DoctrineSpecification\Spec;
 use Shlinkio\Shlink\Core\Entity\Tag;
@@ -62,4 +63,16 @@ class TagRepository extends EntitySpecificationRepository implements TagReposito
 
         return $result > 0;
     }
+
+    public function findOneByNameWithLock(string $name): ?Tag
+    {
+        $qb = $this->createQueryBuilder('t');
+        $qb->where($qb->expr()->eq('t.name', ':name'))
+           ->setParameter('name', $name)
+           ->setMaxResults(1);
+
+        $query = $qb->getQuery()->setLockMode(LockMode::PESSIMISTIC_WRITE);
+
+        return $query->getOneOrNullResult();
+    }
 }
diff --git a/module/Core/src/Repository/TagRepositoryInterface.php b/module/Core/src/Repository/TagRepositoryInterface.php
index 924706ff..b340c1fc 100644
--- a/module/Core/src/Repository/TagRepositoryInterface.php
+++ b/module/Core/src/Repository/TagRepositoryInterface.php
@@ -6,6 +6,7 @@ namespace Shlinkio\Shlink\Core\Repository;
 
 use Doctrine\Persistence\ObjectRepository;
 use Happyr\DoctrineSpecification\Repository\EntitySpecificationRepositoryInterface;
+use Shlinkio\Shlink\Core\Entity\Tag;
 use Shlinkio\Shlink\Core\Tag\Model\TagInfo;
 use Shlinkio\Shlink\Rest\Entity\ApiKey;
 
@@ -19,4 +20,6 @@ interface TagRepositoryInterface extends ObjectRepository, EntitySpecificationRe
     public function findTagsWithInfo(?ApiKey $apiKey = null): array;
 
     public function tagExists(string $tag, ?ApiKey $apiKey = null): bool;
+
+    public function findOneByNameWithLock(string $name): ?Tag;
 }
diff --git a/module/Core/src/ShortUrl/Resolver/PersistenceShortUrlRelationResolver.php b/module/Core/src/ShortUrl/Resolver/PersistenceShortUrlRelationResolver.php
index eb7fddad..b7e27a82 100644
--- a/module/Core/src/ShortUrl/Resolver/PersistenceShortUrlRelationResolver.php
+++ b/module/Core/src/ShortUrl/Resolver/PersistenceShortUrlRelationResolver.php
@@ -8,8 +8,10 @@ use Doctrine\Common\Collections;
 use Doctrine\Common\Collections\Collection;
 use Doctrine\ORM\EntityManagerInterface;
 use Doctrine\ORM\Events;
+use Shlinkio\Shlink\Core\Domain\Repository\DomainRepositoryInterface;
 use Shlinkio\Shlink\Core\Entity\Domain;
 use Shlinkio\Shlink\Core\Entity\Tag;
+use Shlinkio\Shlink\Core\Repository\TagRepositoryInterface;
 
 use function Functional\map;
 use function Functional\unique;
@@ -35,8 +37,9 @@ class PersistenceShortUrlRelationResolver implements ShortUrlRelationResolverInt
             return null;
         }
 
-        /** @var Domain|null $existingDomain */
-        $existingDomain = $this->em->getRepository(Domain::class)->findOneBy(['authority' => $domain]);
+        /** @var DomainRepositoryInterface $repo */
+        $repo = $this->em->getRepository(Domain::class);
+        $existingDomain = $repo->findOneByAuthorityWithLock($domain);
 
         // Memoize only new domains, and let doctrine handle objects hydrated from persistence
         return $existingDomain ?? $this->memoizeNewDomain($domain);
@@ -58,11 +61,12 @@ class PersistenceShortUrlRelationResolver implements ShortUrlRelationResolverInt
         }
 
         $tags = unique($tags);
+        /** @var TagRepositoryInterface $repo */
         $repo = $this->em->getRepository(Tag::class);
 
         return new Collections\ArrayCollection(map($tags, function (string $tagName) use ($repo): Tag {
             // Memoize only new tags, and let doctrine handle objects hydrated from persistence
-            $tag = $repo->findOneBy(['name' => $tagName]) ?? $this->memoizeNewTag($tagName);
+            $tag = $repo->findOneByNameWithLock($tagName) ?? $this->memoizeNewTag($tagName);
             $this->em->persist($tag);
 
             return $tag;
diff --git a/module/Core/test/ShortUrl/Resolver/PersistenceShortUrlRelationResolverTest.php b/module/Core/test/ShortUrl/Resolver/PersistenceShortUrlRelationResolverTest.php
index 8660099c..8698bec0 100644
--- a/module/Core/test/ShortUrl/Resolver/PersistenceShortUrlRelationResolverTest.php
+++ b/module/Core/test/ShortUrl/Resolver/PersistenceShortUrlRelationResolverTest.php
@@ -6,11 +6,11 @@ namespace ShlinkioTest\Shlink\Core\ShortUrl\Resolver;
 
 use Doctrine\Common\EventManager;
 use Doctrine\ORM\EntityManagerInterface;
-use Doctrine\Persistence\ObjectRepository;
 use PHPUnit\Framework\TestCase;
 use Prophecy\Argument;
 use Prophecy\PhpUnit\ProphecyTrait;
 use Prophecy\Prophecy\ObjectProphecy;
+use Shlinkio\Shlink\Core\Domain\Repository\DomainRepositoryInterface;
 use Shlinkio\Shlink\Core\Entity\Domain;
 use Shlinkio\Shlink\Core\Entity\Tag;
 use Shlinkio\Shlink\Core\Repository\TagRepositoryInterface;
@@ -48,8 +48,8 @@ class PersistenceShortUrlRelationResolverTest extends TestCase
      */
     public function findsOrCreatesDomainWhenValueIsProvided(?Domain $foundDomain, string $authority): void
     {
-        $repo = $this->prophesize(ObjectRepository::class);
-        $findDomain = $repo->findOneBy(['authority' => $authority])->willReturn($foundDomain);
+        $repo = $this->prophesize(DomainRepositoryInterface::class);
+        $findDomain = $repo->findOneByAuthorityWithLock($authority)->willReturn($foundDomain);
         $getRepository = $this->em->getRepository(Domain::class)->willReturn($repo->reveal());
 
         $result = $this->resolver->resolveDomain($authority);
@@ -80,7 +80,7 @@ class PersistenceShortUrlRelationResolverTest extends TestCase
         $expectedPersistedTags = count($expectedTags);
 
         $tagRepo = $this->prophesize(TagRepositoryInterface::class);
-        $findTag = $tagRepo->findOneBy(Argument::type('array'))->will(function (array $args): ?Tag {
+        $findTag = $tagRepo->findOneByNameWithLock(Argument::type('string'))->will(function (array $args): ?Tag {
             ['name' => $name] = $args[0];
             return $name === 'foo' ? new Tag($name) : null;
         });
@@ -106,7 +106,7 @@ class PersistenceShortUrlRelationResolverTest extends TestCase
     public function returnsEmptyCollectionWhenProvidingEmptyListOfTags(): void
     {
         $tagRepo = $this->prophesize(TagRepositoryInterface::class);
-        $findTag = $tagRepo->findOneBy(Argument::type('array'))->willReturn(null);
+        $findTag = $tagRepo->findOneByNameWithLock(Argument::type('string'))->willReturn(null);
         $getRepo = $this->em->getRepository(Tag::class)->willReturn($tagRepo->reveal());
         $persist = $this->em->persist(Argument::type(Tag::class));
 
@@ -121,8 +121,8 @@ class PersistenceShortUrlRelationResolverTest extends TestCase
     /** @test */
     public function newDomainsAreMemoizedUntilStateIsCleared(): void
     {
-        $repo = $this->prophesize(ObjectRepository::class);
-        $repo->findOneBy(Argument::type('array'))->willReturn(null);
+        $repo = $this->prophesize(DomainRepositoryInterface::class);
+        $repo->findOneByAuthorityWithLock(Argument::type('string'))->willReturn(null);
         $this->em->getRepository(Domain::class)->willReturn($repo->reveal());
 
         $authority = 'foo.com';
@@ -141,7 +141,7 @@ class PersistenceShortUrlRelationResolverTest extends TestCase
     public function newTagsAreMemoizedUntilStateIsCleared(): void
     {
         $tagRepo = $this->prophesize(TagRepositoryInterface::class);
-        $tagRepo->findOneBy(Argument::type('array'))->willReturn(null);
+        $tagRepo->findOneByNameWithLock(Argument::type('string'))->willReturn(null);
         $this->em->getRepository(Tag::class)->willReturn($tagRepo->reveal());
         $this->em->persist(Argument::type(Tag::class))->will(function (): void {
         });