diff --git a/.rubocop.yml b/.rubocop.yml
index 17fc8fa9..dd69bab0 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -163,4 +163,7 @@ Style/SlicingWithRange:
 Performance/StringIdentifierArgument:
   Exclude:
     - 'test/support/websocket_test_plugin.rb'
-    - 'test/support/requests/plugins/upgrade.rb'
\ No newline at end of file
+    - 'test/support/requests/plugins/upgrade.rb'
+
+Style/Lambda:
+  Enabled: false
diff --git a/lib/httpx/pool.rb b/lib/httpx/pool.rb
index c18c8f61..86797302 100644
--- a/lib/httpx/pool.rb
+++ b/lib/httpx/pool.rb
@@ -14,7 +14,6 @@ module HTTPX
 
     def initialize
       @resolvers = {}
-      @_resolver_ios = {}
       @timers = Timers.new
       @selector = Selector.new
       @connections = []
@@ -111,7 +110,7 @@ module HTTPX
       resolver << connection
       return if resolver.empty?
 
-      @_resolver_ios[resolver] ||= select_connection(resolver)
+      select_connection(resolver)
     end
 
     def on_resolver_connection(connection)
@@ -143,7 +142,6 @@ module HTTPX
       @resolvers.delete(resolver_type)
 
       deselect_connection(resolver)
-      @_resolver_ios.delete(resolver)
       resolver.close unless resolver.closed?
     end
 
diff --git a/sig/pool.rbs b/sig/pool.rbs
index 6006a595..d316a71a 100644
--- a/sig/pool.rbs
+++ b/sig/pool.rbs
@@ -1,14 +1,20 @@
 module HTTPX
   class Pool
+    @resolvers: Hash[Class, Resolver::Resolver]
+    @timers: Timers
+    @selector: Selector
+    @connections: Array[Connection]
+    @connected_connections: Integer
+
     def empty?: () -> void
 
     def next_tick: () -> void
 
-    def close: (*Array[Connection]) -> void
+    def close: (?Array[Connection] connections) -> void
 
-    def init_connection: (Connection, Options) -> void
+    def init_connection: (Connection connection, Options options) -> void
 
-    def find_connection: (generic_uri, Options) -> Connection?
+    def find_connection: (URI::Generic uri, Options options) -> Connection?
 
     def deactivate: (*Array[Connection]) -> void
 
@@ -28,13 +34,13 @@ module HTTPX
 
     def unregister_connection: (Connection) -> void
 
-    def select_connection: (resolver | Connection connection) -> void
+    def select_connection: (Resolver::Resolver | Connection connection) -> void
 
-    def deselect_connection: (resolver | Connection connection) -> void
+    def deselect_connection: (Resolver::Resolver | Connection connection) -> void
 
-    def coalesce_connections: (Connection, Connection) -> void
+    def coalesce_connections: (Connection coalescable, Connection coalescing) -> void
 
-    def next_timeout: () -> Numeric?
+    def next_timeout: () -> (Integer | Float | nil)
 
     def find_resolver_for: (Connection) -> Resolver::Resolver
   end