diff --git a/.gitignore b/.gitignore
index 3a9875b..6de133d 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,4 @@
 /vendor/
 composer.lock
+.phpunit.result.cache
+/test
diff --git a/README.md b/README.md
index 882353b..182be1a 100644
--- a/README.md
+++ b/README.md
@@ -1,4 +1,4 @@
-Optimize Composer for Drupal 8.5+ projects
+Optimize Composer for Drupal projects
 ====
 [![Build Status](https://travis-ci.org/zaporylie/composer-drupal-optimizations.svg?branch=master)](https://travis-ci.org/zaporylie/composer-drupal-optimizations)
 ![Packagist](https://img.shields.io/packagist/v/zaporylie/composer-drupal-optimizations.svg)
@@ -18,9 +18,7 @@ No configuration required 🎊
 
 # Optimizations
 
-- Reduce memory usage and CPU usage by removing legacy symfony tags (see also https://github.com/symfony/flex/pull/378) 
-
-(only one at the moment)
+- Reduce memory usage and CPU usage by removing legacy symfony tags
 
 # Benchmark
 
@@ -29,15 +27,41 @@ Following numbers are for clean https://github.com/drupal-composer/drupal-projec
 Before:
 
 ```
-Memory usage: 304.16MB (peak: 876.79MB), time: 17.13s
+Memory usage: 323.19MB (peak: 1121.09MB), time: 13.68s
 ```
 
 After:
 
 ```
-Memory usage: 218.72MB (peak: 250.44MB), time: 4.83s
+Memory usage: 238.66MB (peak: 297.17MB), time: 4.84s
+```
+
+> php 7.2, macOS High Sierra, i7, 16GB RAM
+
+# Configuration
+
+If no configuration is provided this package will provide sensible defaults based on the content of project's composer.json
+file. Default configuration should cover 99% of the cases. However, in case you want to manually specify the tags
+that should be filtered out you are welcome to use the `extra` section:
+
+```json
+{
+  "extra": {
+    "composer-drupal-optimizations": {
+      "require": {
+        "symfony/symfony": ">3.4"
+      }
+    }
+  }
+}
 ```
 
+***Recommendation note:***
+Use defaults (skip config above) if possible - this package will be maintained throughout the Drupal's lifecycle in order
+to optimize legacy constraints in parallel with Drupal's requirements.
+
+All you have to do is to make sure your drupal core constraint is set to `drupal/core: ^8.5` or above.
+
 # Credits
 
 - Symfony community - idea and development; Special thanks to @nicolas-grekas
diff --git a/src/Cache.php b/src/Cache.php
index c410aa9..815b432 100644
--- a/src/Cache.php
+++ b/src/Cache.php
@@ -3,6 +3,8 @@
 namespace zaporylie\ComposerDrupalOptimizations;
 
 use Composer\Cache as BaseCache;
+use Composer\Semver\Constraint\Constraint;
+use Composer\Semver\VersionParser;
 
 /**
  * Class Cache
@@ -10,17 +12,27 @@
  */
 class Cache extends BaseCache
 {
-    protected static $lowestTags = [
-        'symfony/symfony' => 'v3.4.0',
-    ];
 
+    /**
+     * @var array
+     */
+    protected $packages = [];
+
+    /**
+     * @var \Composer\Semver\VersionParser
+     */
+    protected $versionParser;
+
+    /**
+     * {@inheritdoc}
+     */
     public function read($file)
     {
         $content = $this->readFile($file);
         if (!\is_array($data = json_decode($content, true))) {
             return $content;
         }
-        foreach (array_keys(static::$lowestTags) as $key) {
+        foreach (array_keys($this->packages) as $key) {
             list($provider, ) = explode('/', $key, 2);
             if (0 === strpos($file, "provider-$provider\$")) {
                 $data = $this->removeLegacyTags($data);
@@ -35,21 +47,81 @@ protected function readFile($file)
         return parent::read($file);
     }
 
+    /**
+     * Removes legacy tags from $data.
+     *
+     * @param array $data
+     * @return array
+     */
     public function removeLegacyTags(array $data)
     {
-        foreach (self::$lowestTags as $package => $lowestVersion) {
-            if (!isset($data['packages'][$package][$lowestVersion])) {
+        // Skip if the list of packages is empty.
+        if (!$this->packages || empty($data['packages'])) {
+            return $data;
+        }
+
+        // Skip if none of the packages was found.
+        if (!array_diff_key($data['packages'], $this->packages)) {
+            return $data;
+        }
+
+        foreach ($this->packages as $packageName => $packageVersionConstraint) {
+            if (!isset($data['packages'][$packageName])) {
                 continue;
             }
-            foreach ($data['packages'] as $package => $versions) {
-                foreach ($versions as $version => $composerJson) {
-                    if (version_compare($version, $lowestVersion, '<')) {
-                        unset($data['packages'][$package][$version]);
-                    }
+            $packages = [];
+            $specificPackage = $data['packages'][$packageName];
+            foreach ($specificPackage as $version => $composerJson) {
+                if ('dev-master' === $version) {
+                    $normalizedVersion = $this->versionParser->normalize($composerJson['extra']['branch-alias']['dev-master']);
+                } else {
+                    $normalizedVersion = $composerJson['version_normalized'];
+                }
+                $packageConstraint = $this->versionParser->parseConstraints($packageVersionConstraint);
+                $versionConstraint = new Constraint('==', $normalizedVersion);
+                if ($packageConstraint->matches($versionConstraint)) {
+                    $packages += isset($composerJson['replace']) ? $composerJson['replace'] : [];
+                } else {
+                    unset($specificPackage[$version]);
+                }
+            }
+
+            // Ignore requirements: their intersection with versions of the package gives empty result.
+            if (!$specificPackage) {
+                continue;
+            }
+            $data['packages'][$packageName] = $specificPackage;
+
+            unset($specificPackage['dev-master']);
+            foreach ($data['packages'] as $name => $versions) {
+                if (!isset($packages[$name]) || null === $devMasterAlias = (isset($versions['dev-master']['extra']['branch-alias']['dev-master']) ? $versions['dev-master']['extra']['branch-alias']['dev-master'] : null)) {
+                    continue;
+                }
+                $devMaster = $versions['dev-master'];
+                $versions = array_intersect_key($versions, $specificPackage);
+                $packageConstraint = $this->versionParser->parseConstraints($packageVersionConstraint);
+                $versionConstraint = new Constraint('==', $this->versionParser->normalize($devMasterAlias));
+                if ($packageConstraint->matches($versionConstraint)) {
+                    $versions['dev-master'] = $devMaster;
+                }
+                if ($versions) {
+                    $data['packages'][$name] = $versions;
                 }
             }
-            break;
         }
         return $data;
+
+    }
+
+    /**
+     * @param array $packages
+     *
+     * @return $this
+     */
+    public function setRequiredVersionConstraints(array $packages) {
+        $this->versionParser = new VersionParser();
+        $this->packages = $packages;
+        return $this;
     }
+
 }
diff --git a/src/Plugin.php b/src/Plugin.php
index b7537be..7069aac 100644
--- a/src/Plugin.php
+++ b/src/Plugin.php
@@ -8,24 +8,64 @@
 use Composer\Plugin\PluginInterface;
 use Composer\Repository\RepositoryFactory;
 use Composer\Repository\RepositoryManager;
+use Composer\Semver\Constraint\Constraint;
+use Composer\Semver\Constraint\ConstraintInterface;
 
 class Plugin implements PluginInterface
 {
+
     public function activate(Composer $composer, IOInterface $io)
     {
+        // Set default version constraints based on the composer requirements.
+        $extra = $composer->getPackage()->getExtra();
+        $packages = $composer->getPackage()->getRequires();
+        if (!isset($extra['composer-drupal-optimizations']['require']) && isset($packages['drupal/core'])) {
+            $coreConstraint = $packages['drupal/core']->getConstraint();
+            $extra['composer-drupal-optimizations']['require'] = static::getDefaultRequire($coreConstraint);
+            if (!empty($extra['composer-drupal-optimizations']['require']) && $io->isVerbose()) {
+                $io->write('Required tags were not explicitly set so the zaporylie/composer-drupal-optimizations set default based on project\'s composer.json content.');
+            }
+        }
+        if (!empty($extra['composer-drupal-optimizations']['require']) && $io->isVerbose()) {
+            foreach ($extra['composer-drupal-optimizations']['require'] as $package => $version) {
+                $io->write(sprintf('extra.commerce-drupal-optimizations.require.%s: \'%s\'', $package, $version));
+            }
+        }
+
         $rfs = Factory::createRemoteFilesystem($io, $composer->getConfig());
         $manager = RepositoryFactory::manager($io, $composer->getConfig(), $composer->getEventDispatcher(), $rfs);
-        $setRepositories = \Closure::bind(function (RepositoryManager $manager) {
+        $setRepositories = \Closure::bind(function (RepositoryManager $manager) use ($extra) {
             $manager->repositoryClasses = $this->repositoryClasses;
             $manager->setRepositoryClass('composer', TruncatedComposerRepository::class);
             $manager->repositories = $this->repositories;
             $i = 0;
             foreach (RepositoryFactory::defaultRepos(null, $this->config, $manager) as $repo) {
                 $manager->repositories[$i++] = $repo;
+                if ($repo instanceof TruncatedComposerRepository && !empty($extra['composer-drupal-optimizations']['require'])) {
+                  $repo->setRequiredVersionConstraints($extra['composer-drupal-optimizations']['require']);
+                }
             }
             $manager->setLocalRepository($this->getLocalRepository());
         }, $composer->getRepositoryManager(), RepositoryManager::class);
         $setRepositories($manager);
         $composer->setRepositoryManager($manager);
     }
+
+    /**
+     * Negotiates default require constraint and package for given drupal/core.
+     *
+     * @param \Composer\Semver\Constraint\ConstraintInterface
+     *
+     * @return array
+     */
+    static public function getDefaultRequire(ConstraintInterface $coreConstraint)
+    {
+        if ((new Constraint('>=', '8.5.0'))->matches($coreConstraint)
+          && !(new Constraint('<', '8.5.0'))->matches($coreConstraint)) {
+            return [
+              'symfony/symfony' => '>3.4',
+            ];
+        }
+        return [];
+    }
 }
diff --git a/src/TruncatedComposerRepository.php b/src/TruncatedComposerRepository.php
index 0b99bab..23f8ecf 100644
--- a/src/TruncatedComposerRepository.php
+++ b/src/TruncatedComposerRepository.php
@@ -18,6 +18,9 @@ public function __construct(array $repoConfig, IOInterface $io, Config $config,
     protected function fetchFile($filename, $cacheKey = null, $sha256 = null, $storeLastModifiedTime = false)
     {
         $data = parent::fetchFile($filename, $cacheKey, $sha256, $storeLastModifiedTime);
-        return $this->cache->removeLegacyTags($data);
+        return \is_array($data) ? $this->cache->removeLegacyTags($data) : $data;
+    }
+    public function setRequiredVersionConstraints(array $packages) {
+        $this->cache->setRequiredVersionConstraints($packages);
     }
 }
diff --git a/tests/CacheTest.php b/tests/CacheTest.php
index 94e8063..2eb471f 100644
--- a/tests/CacheTest.php
+++ b/tests/CacheTest.php
@@ -17,11 +17,12 @@ class CacheTest extends TestCase
      * @param $expected
      *
      * @dataProvider provideReadTest
+     * @covers \zaporylie\ComposerDrupalOptimizations\Cache::read
      */
     public function testRead($provided, $expected)
     {
         $cache = new class(new NullIO(), 'test') extends Cache {
-            protected static $lowestTags = [
+            protected $packages = [
               'vendor/package' => 'version',
             ];
             protected function readFile($file)
@@ -52,4 +53,109 @@ function provideReadTest()
         yield 'matching-incorrect-provider' => ['{"provider":"vendor"}', '{"provider":"vendor"}'];
         yield 'matching' => ['provider-vendor${"provider":"vendor"}', '{"provider":"vendor","status":"ok"}'];
     }
+
+    /**
+     * @dataProvider provideRemoveLegacyTags
+     * @covers \zaporylie\ComposerDrupalOptimizations\Cache::removeLegacyTags
+     */
+    public function testRemoveLegacyTags(array $expected, array $packages, array $versionConstraints)
+    {
+        /** @var Cache $cache */
+        $cache = (new \ReflectionClass(Cache::class))->newInstanceWithoutConstructor();
+        $cache->setRequiredVersionConstraints($versionConstraints);
+        $this->assertSame(['packages' => $expected], $cache->removeLegacyTags(['packages' => $packages]));
+    }
+
+    /**
+     * Test data.
+     */
+    public function provideRemoveLegacyTags()
+    {
+        yield 'no-symfony/symfony' => [[123], [123], ['symfony/symfony' => '~1']];
+        $branchAlias = function ($versionAlias) {
+            return [
+              'extra' => [
+                'branch-alias' => [
+                  'dev-master' => $versionAlias.'-dev',
+                ],
+              ],
+            ];
+        };
+        $packages = [
+          'foo/unrelated' => [
+            '1.0.0' => [],
+          ],
+          'symfony/symfony' => [
+            '3.3.0' => [
+              'version_normalized' => '3.3.0.0',
+              'replace' => ['symfony/foo' => 'self.version'],
+            ],
+            '3.4.0' => [
+              'version_normalized' => '3.4.0.0',
+              'replace' => ['symfony/foo' => 'self.version'],
+            ],
+            'dev-master' => $branchAlias('3.5') + [
+                'replace' => ['symfony/foo' => 'self.version'],
+              ],
+          ],
+          'symfony/foo' => [
+            '3.3.0' => ['version_normalized' => '3.3.0.0'],
+            '3.4.0' => ['version_normalized' => '3.4.0.0'],
+            'dev-master' => $branchAlias('3.5'),
+          ],
+        ];
+        yield 'empty-intersection-ignores' => [$packages, $packages, ['symfony/symfony' => '~2.0']];
+        yield 'empty-intersection-ignores' => [$packages, $packages, ['symfony/symfony' => '~4.0']];
+        $expected = $packages;
+        unset($expected['symfony/symfony']['3.3.0']);
+        unset($expected['symfony/foo']['3.3.0']);
+        yield 'non-empty-intersection-filters' => [$expected, $packages, ['symfony/symfony' => '~3.4']];
+        unset($expected['symfony/symfony']['3.4.0']);
+        unset($expected['symfony/foo']['3.4.0']);
+        yield 'master-only' => [$expected, $packages, ['symfony/symfony' => '~3.5']];
+        $packages = [
+          'symfony/symfony' => [
+            '2.8.0' => [
+              'version_normalized' => '2.8.0.0',
+              'replace' => [
+                'symfony/legacy' => 'self.version',
+                'symfony/foo' => 'self.version',
+              ],
+            ],
+          ],
+          'symfony/legacy' => [
+            '2.8.0' => ['version_normalized' => '2.8.0.0'],
+            'dev-master' => $branchAlias('2.8'),
+          ],
+        ];
+        yield 'legacy-are-not-filtered' => [$packages, $packages, ['symfony/symfony' => '~3.0']];
+        $packages = [
+          'symfony/symfony' => [
+            '2.8.0' => [
+              'version_normalized' => '2.8.0.0',
+              'replace' => [
+                'symfony/foo' => 'self.version',
+                'symfony/new' => 'self.version',
+              ],
+            ],
+            'dev-master' => $branchAlias('3.0') + [
+                'replace' => [
+                  'symfony/foo' => 'self.version',
+                  'symfony/new' => 'self.version',
+                ],
+              ],
+          ],
+          'symfony/foo' => [
+            '2.8.0' => ['version_normalized' => '2.8.0.0'],
+            'dev-master' => $branchAlias('3.0'),
+          ],
+          'symfony/new' => [
+            'dev-master' => $branchAlias('3.0'),
+          ],
+        ];
+        $expected = $packages;
+        unset($expected['symfony/symfony']['dev-master']);
+        unset($expected['symfony/foo']['dev-master']);
+        yield 'master-is-filtered-only-when-in-range' => [$expected, $packages, ['symfony/symfony' => '~2.8']];
+    }
 }
diff --git a/tests/DefaultRequireTest.php b/tests/DefaultRequireTest.php
new file mode 100644
index 0000000..e3368c4
--- /dev/null
+++ b/tests/DefaultRequireTest.php
@@ -0,0 +1,40 @@
+<?php
+
+namespace zaporylie\ComposerDrupalOptimizations\Tests;
+
+use Composer\Semver\VersionParser;
+use PHPUnit\Framework\TestCase;
+use zaporylie\ComposerDrupalOptimizations\Plugin;
+
+class DefaultRequireTest extends TestCase
+{
+
+    /**
+     * Tests default require provider.
+     *
+     * @param $provided
+     * @param $expected
+     * @dataProvider provideTestData
+     */
+    public function testDefaultRequire($provided, $expected)
+    {
+        $versionParser = new VersionParser();
+        self::assertEquals($expected, Plugin::getDefaultRequire($versionParser->parseConstraints($provided)));
+    }
+
+    /**
+     * Test data.
+     */
+    function provideTestData()
+    {
+        yield 'exact-below' => ['8.2.0', []];
+        yield 'exact-above' => ['8.6.0', ['symfony/symfony' => '>3.4']];
+        yield 'exact-min' => ['8.5.0', ['symfony/symfony' => '>3.4']];
+        yield 'range-below' => ['~8.4.0', []];
+        yield 'range-overlapping' => ['>8.4.0 <8.6.0', []];
+        yield 'range-below-above' => ['~8.2.0|~8.6.0', []];
+        yield 'range-above' => ['~8.6.0', ['symfony/symfony' => '>3.4']];
+        yield 'range-min' => ['^8.5', ['symfony/symfony' => '>3.4']];
+    }
+
+}