From a96b25fb05e52295e42578539939e170c8ab8530 Mon Sep 17 00:00:00 2001
From: Dzmitry Shuiski <errfrom@yandex.ru>
Date: Thu, 6 Nov 2025 16:31:26 +0100
Subject: [PATCH 1/5] Limit the number of parallel requests to Ogmios

---
 spago-packages.nix               | 48 ++++++++------------------------
 spago.dhall                      |  1 +
 src/Kupmios/KupmiosM.purs        | 40 +++++++++++++++++++++-----
 src/Kupmios/KupmiosM/Kupo.purs   |  4 +--
 src/Kupmios/KupmiosM/Ogmios.purs | 19 +++++++++----
 src/Kupmios/Provider.purs        |  3 +-
 src/KupmiosProvider.purs         |  1 +
 7 files changed, 63 insertions(+), 53 deletions(-)

diff --git a/spago-packages.nix b/spago-packages.nix
index dff13e4..8acd10e 100644
--- a/spago-packages.nix
+++ b/spago-packages.nix
@@ -185,18 +185,6 @@ let
         installPhase = "ln -s $src $out";
       };
 
-    "cardano-collateral-select" = pkgs.stdenv.mkDerivation {
-        name = "cardano-collateral-select";
-        version = "v1.0.0";
-        src = pkgs.fetchgit {
-          url = "https://github.com/mlabs-haskell/purescript-cardano-collateral-select";
-          rev = "193bf49be979b42aa1f0f9cb3d7582d6bc98e3b9";
-          sha256 = "1jbl6k779brbqzf7jf80is63b23k3mqzf2mzr222qswd3wg8s5b0";
-        };
-        phases = "installPhase";
-        installPhase = "ln -s $src $out";
-      };
-
     "cardano-data-lite" = pkgs.stdenv.mkDerivation {
         name = "cardano-data-lite";
         version = "070a1a502472211853099c2566a7e9100a7b1a61";
@@ -209,30 +197,6 @@ let
         installPhase = "ln -s $src $out";
       };
 
-    "cardano-key-wallet" = pkgs.stdenv.mkDerivation {
-        name = "cardano-key-wallet";
-        version = "v2.0.0";
-        src = pkgs.fetchgit {
-          url = "https://github.com/mlabs-haskell/purescript-cardano-key-wallet";
-          rev = "99d9bb7c8b291ad0bc9709d493ff7e02d14a89c0";
-          sha256 = "11jw05s7vpgg6bdyi3zy4z1fcj53a8kaaja5717b7yjgflmhfn8s";
-        };
-        phases = "installPhase";
-        installPhase = "ln -s $src $out";
-      };
-
-    "cardano-message-signing" = pkgs.stdenv.mkDerivation {
-        name = "cardano-message-signing";
-        version = "v1.0.0";
-        src = pkgs.fetchgit {
-          url = "https://github.com/mlabs-haskell/purescript-cardano-message-signing";
-          rev = "97f6f97a258ae3490df0be6b39fa6769677aa04f";
-          sha256 = "1ns7m9awn4w5amvf9ffldxk7acm73fg8clw4hja4nnl61mskqr5w";
-        };
-        phases = "installPhase";
-        installPhase = "ln -s $src $out";
-      };
-
     "cardano-plutus-data-schema" = pkgs.stdenv.mkDerivation {
         name = "cardano-plutus-data-schema";
         version = "110ba00261b1480895f8412016c639ea655412f6";
@@ -281,6 +245,18 @@ let
         installPhase = "ln -s $src $out";
       };
 
+    "concurrent-queues" = pkgs.stdenv.mkDerivation {
+        name = "concurrent-queues";
+        version = "v3.0.0";
+        src = pkgs.fetchgit {
+          url = "https://github.com/purescript-contrib/purescript-concurrent-queues.git";
+          rev = "905a0cb902dec070fa621819455363660de289c4";
+          sha256 = "0wr9fkdf23mam4ip7nwdm1i7qy0l1lysyfkffbqj07dvrgpkzd0f";
+        };
+        phases = "installPhase";
+        installPhase = "ln -s $src $out";
+      };
+
     "console" = pkgs.stdenv.mkDerivation {
         name = "console";
         version = "v6.0.0";
diff --git a/spago.dhall b/spago.dhall
index a940441..b6e370e 100644
--- a/spago.dhall
+++ b/spago.dhall
@@ -9,6 +9,7 @@
   , "cardano-provider"
   , "cardano-data-lite"
   , "cardano-types"
+  , "concurrent-queues"
   , "console"
   , "control"
   , "datetime"
diff --git a/src/Kupmios/KupmiosM.purs b/src/Kupmios/KupmiosM.purs
index 1ab6a6a..7c72d58 100644
--- a/src/Kupmios/KupmiosM.purs
+++ b/src/Kupmios/KupmiosM.purs
@@ -7,16 +7,22 @@ module Cardano.Kupmios.KupmiosM
   , ParKupmiosM
   , KupmiosMT(KupmiosMT)
   , handleAffjaxResponse
+  , mkKupmiosEnv
   ) where
 
 import Prelude
 
 import Aeson (class DecodeAeson, decodeAeson, parseJsonStringToAeson)
 import Affjax (Error, Response) as Affjax
+import Cardano.Kupmios.Helpers (logWithLevel)
+import Cardano.Kupmios.KupmiosM.HttpUtils (handleAffjaxResponseGeneric)
 import Cardano.Provider.Error
   ( ClientError(ClientHttpError, ClientHttpResponseError, ClientDecodeJsonError)
   , ServiceError(ServiceOtherError)
   )
+import Cardano.Provider.ServerConfig (ServerConfig)
+import Concurrent.Queue (Queue)
+import Concurrent.Queue (new, write) as Queue
 import Control.Alt (class Alt)
 import Control.Alternative (class Alternative)
 import Control.Monad.Error.Class (class MonadError, class MonadThrow)
@@ -26,15 +32,13 @@ import Control.Monad.Reader.Trans (ReaderT(ReaderT), asks)
 import Control.Monad.Rec.Class (class MonadRec)
 import Control.Parallel (class Parallel, parallel, sequential)
 import Control.Plus (class Plus)
-import Cardano.Kupmios.Helpers (logWithLevel)
-import Cardano.Kupmios.KupmiosM.HttpUtils (handleAffjaxResponseGeneric)
-
-import Cardano.Provider.ServerConfig (ServerConfig)
+import Data.Array ((..))
 import Data.Either (Either)
 import Data.Log.Level (LogLevel)
 import Data.Log.Message (Message)
-import Data.Maybe (Maybe, fromMaybe)
+import Data.Maybe (Maybe(Just, Nothing), fromMaybe)
 import Data.Newtype (class Newtype, unwrap, wrap)
+import Data.Traversable (traverse_)
 import Effect.Aff (Aff, ParAff)
 import Effect.Aff.Class (class MonadAff, liftAff)
 import Effect.Class (class MonadEffect)
@@ -48,8 +52,13 @@ import Effect.Exception (Error)
 -- | - logging level
 -- | - optional custom logger
 type KupmiosConfig =
-  { ogmiosConfig :: ServerConfig
-  , kupoConfig :: ServerConfig
+  { ogmios ::
+      { serverConfig :: ServerConfig
+      , maxParallelRequests :: Maybe Int
+      }
+  , kupo ::
+      { serverConfig :: ServerConfig
+      }
   , logLevel :: LogLevel
   , customLogger :: Maybe (LogLevel -> Message -> Aff Unit)
   , suppressLogs :: Boolean
@@ -58,8 +67,25 @@ type KupmiosConfig =
 -- | `KupmiosEnv` contains everything needed for `KupmiosM` to run.
 type KupmiosEnv =
   { config :: KupmiosConfig
+  , ogmiosRequestSemaphore :: Maybe (Queue Unit)
   }
 
+mkKupmiosEnv :: KupmiosConfig -> Aff KupmiosEnv
+mkKupmiosEnv config =
+  case config.ogmios.maxParallelRequests of
+    Nothing ->
+      pure
+        { config
+        , ogmiosRequestSemaphore: Nothing
+        }
+    Just n -> do
+      sem <- Queue.new
+      traverse_ (const (Queue.write sem unit)) $ 1 .. n
+      pure
+        { config
+        , ogmiosRequestSemaphore: Just sem
+        }
+
 type KupmiosM = KupmiosMT Aff
 
 type ParKupmiosM = KupmiosMT ParAff
diff --git a/src/Kupmios/KupmiosM/Kupo.purs b/src/Kupmios/KupmiosM/Kupo.purs
index 76fb09d..3d5049d 100644
--- a/src/Kupmios/KupmiosM/Kupo.purs
+++ b/src/Kupmios/KupmiosM/Kupo.purs
@@ -156,7 +156,7 @@ getScriptByHash scriptHash = do
 -- https://github.com/Plutonomicon/cardano-transaction-lib/issues/1293
 isTxConfirmed :: TransactionHash -> KupmiosM (Either ClientError (Maybe Slot))
 isTxConfirmed txHash = do
-  config <- asks (_.kupoConfig <<< _.config)
+  config <- asks (_.serverConfig <<< _.kupo <<< _.config)
   do
     -- we don't add `?unspent`, because we only care about existence of UTxOs,
     -- possibly they can be consumed
@@ -493,7 +493,7 @@ unwrapKupoAuxData (KupoAuxiliaryData mAuxData) = mAuxData
 kupoGetRequest
   :: String -> KupmiosM (Either Affjax.Error (Affjax.Response String))
 kupoGetRequest endpoint = do
-  config <- asks (_.kupoConfig <<< _.config)
+  config <- asks (_.serverConfig <<< _.kupo <<< _.config)
   logTrace' $ "sending kupo request: " <> endpoint
   liftAff $ kupoGetRequestAff config endpoint
 
diff --git a/src/Kupmios/KupmiosM/Ogmios.purs b/src/Kupmios/KupmiosM/Ogmios.purs
index f6e2585..f8c8967 100644
--- a/src/Kupmios/KupmiosM/Ogmios.purs
+++ b/src/Kupmios/KupmiosM/Ogmios.purs
@@ -46,8 +46,9 @@ import Cardano.Provider.ServerConfig (ServerConfig, mkHttpUrl)
 import Cardano.Types.CborBytes (CborBytes)
 import Cardano.Types.Chain as Chain
 import Cardano.Types.TransactionHash (TransactionHash)
+import Concurrent.Queue (read, write) as Queue
 import Control.Monad.Error.Class (class MonadThrow, throwError)
-import Control.Monad.Reader.Class (asks)
+import Control.Monad.Reader.Class (ask)
 import Data.ByteArray (byteArrayToHex)
 import Data.Either (Either(Left), either, hush)
 import Data.HTTP.Method (Method(POST))
@@ -56,7 +57,7 @@ import Data.Maybe (Maybe(Just, Nothing))
 import Data.Newtype (unwrap, wrap)
 import Data.Time.Duration (Milliseconds(Milliseconds))
 import Data.Tuple.Nested (type (/\), (/\))
-import Effect.Aff (Aff, delay)
+import Effect.Aff (Aff, bracket, delay)
 import Effect.Aff.Class (class MonadAff, liftAff)
 import Effect.Exception (Error, error)
 
@@ -159,11 +160,17 @@ ogmiosPostRequest
   :: Aeson -- ^ JSON-RPC request body
   -> KupmiosM (Either Affjax.Error (Affjax.Response String))
 ogmiosPostRequest body = do
-  config <- asks (_.ogmiosConfig <<< _.config)
+  { config: { ogmios: { serverConfig } }, ogmiosRequestSemaphore } <- ask
   logTrace' $ "sending ogmios HTTP request: " <> show body
-  s <- liftAff $ ogmiosPostRequestAff config body
-  logTrace' $ "response: " <> (show $ hush $ s)
-  pure s
+  let request = ogmiosPostRequestAff serverConfig body
+  resp <-
+    liftAff case ogmiosRequestSemaphore of
+      Just sem ->
+        bracket (Queue.read sem) (const (Queue.write sem unit)) $ const request
+      Nothing ->
+        request
+  logTrace' $ "response: " <> (show $ hush resp)
+  pure resp
 
 ogmiosPostRequestAff
   :: ServerConfig
diff --git a/src/Kupmios/Provider.purs b/src/Kupmios/Provider.purs
index 95d0321..0a1da1a 100644
--- a/src/Kupmios/Provider.purs
+++ b/src/Kupmios/Provider.purs
@@ -34,8 +34,7 @@ import Data.Maybe (isJust)
 import Data.Newtype (unwrap, wrap)
 import Effect.Aff (Aff)
 
-providerForKupmiosBackend
-  :: (forall (a :: Type). KupmiosM a -> Aff a) -> Provider
+providerForKupmiosBackend :: (forall (a :: Type). KupmiosM a -> Aff a) -> Provider
 providerForKupmiosBackend runKupmiosM =
   { getDatumByHash: runKupmiosM <<< Kupo.getDatumByHash
   , getScriptByHash: runKupmiosM <<< Kupo.getScriptByHash
diff --git a/src/KupmiosProvider.purs b/src/KupmiosProvider.purs
index 93423f5..511ef4d 100644
--- a/src/KupmiosProvider.purs
+++ b/src/KupmiosProvider.purs
@@ -7,6 +7,7 @@ import Cardano.Kupmios.KupmiosM
   , KupmiosM
   , KupmiosMT(KupmiosMT)
   , handleAffjaxResponse
+  , mkKupmiosEnv
   ) as X
 import Cardano.Kupmios.Kupo
   ( getDatumByHash

From 937f4091b721bc3bc27df460029495dcdafd1c0d Mon Sep 17 00:00:00 2001
From: Dzmitry Shuiski <errfrom@yandex.ru>
Date: Fri, 7 Nov 2025 15:17:58 +0100
Subject: [PATCH 2/5] Refactor KupmiosEnv initialization interface

---
 src/Kupmios/KupmiosM.purs        | 33 +++++++++-----------------------
 src/Kupmios/KupmiosM/Kupo.purs   |  4 ++--
 src/Kupmios/KupmiosM/Ogmios.purs |  4 ++--
 src/KupmiosProvider.purs         |  2 +-
 4 files changed, 14 insertions(+), 29 deletions(-)

diff --git a/src/Kupmios/KupmiosM.purs b/src/Kupmios/KupmiosM.purs
index 7c72d58..b6edc89 100644
--- a/src/Kupmios/KupmiosM.purs
+++ b/src/Kupmios/KupmiosM.purs
@@ -7,7 +7,7 @@ module Cardano.Kupmios.KupmiosM
   , ParKupmiosM
   , KupmiosMT(KupmiosMT)
   , handleAffjaxResponse
-  , mkKupmiosEnv
+  , initOgmiosRequestSemaphore
   ) where
 
 import Prelude
@@ -36,7 +36,7 @@ import Data.Array ((..))
 import Data.Either (Either)
 import Data.Log.Level (LogLevel)
 import Data.Log.Message (Message)
-import Data.Maybe (Maybe(Just, Nothing), fromMaybe)
+import Data.Maybe (Maybe, fromMaybe)
 import Data.Newtype (class Newtype, unwrap, wrap)
 import Data.Traversable (traverse_)
 import Effect.Aff (Aff, ParAff)
@@ -52,13 +52,8 @@ import Effect.Exception (Error)
 -- | - logging level
 -- | - optional custom logger
 type KupmiosConfig =
-  { ogmios ::
-      { serverConfig :: ServerConfig
-      , maxParallelRequests :: Maybe Int
-      }
-  , kupo ::
-      { serverConfig :: ServerConfig
-      }
+  { ogmiosConfig :: ServerConfig
+  , kupoConfig :: ServerConfig
   , logLevel :: LogLevel
   , customLogger :: Maybe (LogLevel -> Message -> Aff Unit)
   , suppressLogs :: Boolean
@@ -70,21 +65,11 @@ type KupmiosEnv =
   , ogmiosRequestSemaphore :: Maybe (Queue Unit)
   }
 
-mkKupmiosEnv :: KupmiosConfig -> Aff KupmiosEnv
-mkKupmiosEnv config =
-  case config.ogmios.maxParallelRequests of
-    Nothing ->
-      pure
-        { config
-        , ogmiosRequestSemaphore: Nothing
-        }
-    Just n -> do
-      sem <- Queue.new
-      traverse_ (const (Queue.write sem unit)) $ 1 .. n
-      pure
-        { config
-        , ogmiosRequestSemaphore: Just sem
-        }
+initOgmiosRequestSemaphore :: Int -> Aff (Queue Unit)
+initOgmiosRequestSemaphore maxParallelRequests = do
+  sem <- Queue.new
+  traverse_ (const (Queue.write sem unit)) $ 1 .. maxParallelRequests
+  pure sem
 
 type KupmiosM = KupmiosMT Aff
 
diff --git a/src/Kupmios/KupmiosM/Kupo.purs b/src/Kupmios/KupmiosM/Kupo.purs
index 3d5049d..76fb09d 100644
--- a/src/Kupmios/KupmiosM/Kupo.purs
+++ b/src/Kupmios/KupmiosM/Kupo.purs
@@ -156,7 +156,7 @@ getScriptByHash scriptHash = do
 -- https://github.com/Plutonomicon/cardano-transaction-lib/issues/1293
 isTxConfirmed :: TransactionHash -> KupmiosM (Either ClientError (Maybe Slot))
 isTxConfirmed txHash = do
-  config <- asks (_.serverConfig <<< _.kupo <<< _.config)
+  config <- asks (_.kupoConfig <<< _.config)
   do
     -- we don't add `?unspent`, because we only care about existence of UTxOs,
     -- possibly they can be consumed
@@ -493,7 +493,7 @@ unwrapKupoAuxData (KupoAuxiliaryData mAuxData) = mAuxData
 kupoGetRequest
   :: String -> KupmiosM (Either Affjax.Error (Affjax.Response String))
 kupoGetRequest endpoint = do
-  config <- asks (_.serverConfig <<< _.kupo <<< _.config)
+  config <- asks (_.kupoConfig <<< _.config)
   logTrace' $ "sending kupo request: " <> endpoint
   liftAff $ kupoGetRequestAff config endpoint
 
diff --git a/src/Kupmios/KupmiosM/Ogmios.purs b/src/Kupmios/KupmiosM/Ogmios.purs
index f8c8967..02a69fc 100644
--- a/src/Kupmios/KupmiosM/Ogmios.purs
+++ b/src/Kupmios/KupmiosM/Ogmios.purs
@@ -160,9 +160,9 @@ ogmiosPostRequest
   :: Aeson -- ^ JSON-RPC request body
   -> KupmiosM (Either Affjax.Error (Affjax.Response String))
 ogmiosPostRequest body = do
-  { config: { ogmios: { serverConfig } }, ogmiosRequestSemaphore } <- ask
+  { config: { ogmiosConfig }, ogmiosRequestSemaphore } <- ask
   logTrace' $ "sending ogmios HTTP request: " <> show body
-  let request = ogmiosPostRequestAff serverConfig body
+  let request = ogmiosPostRequestAff ogmiosConfig body
   resp <-
     liftAff case ogmiosRequestSemaphore of
       Just sem ->
diff --git a/src/KupmiosProvider.purs b/src/KupmiosProvider.purs
index 511ef4d..510195b 100644
--- a/src/KupmiosProvider.purs
+++ b/src/KupmiosProvider.purs
@@ -7,7 +7,7 @@ import Cardano.Kupmios.KupmiosM
   , KupmiosM
   , KupmiosMT(KupmiosMT)
   , handleAffjaxResponse
-  , mkKupmiosEnv
+  , initOgmiosRequestSemaphore
   ) as X
 import Cardano.Kupmios.Kupo
   ( getDatumByHash

From 51a0b8e8662f7f96b2ffd7c8866c5d38d691b421 Mon Sep 17 00:00:00 2001
From: Dzmitry Shuiski <errfrom@yandex.ru>
Date: Fri, 7 Nov 2025 15:22:54 +0100
Subject: [PATCH 3/5] Update signature of initOgmiosRequestSemaphore

---
 src/Kupmios/KupmiosM.purs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/Kupmios/KupmiosM.purs b/src/Kupmios/KupmiosM.purs
index b6edc89..d753ec3 100644
--- a/src/Kupmios/KupmiosM.purs
+++ b/src/Kupmios/KupmiosM.purs
@@ -65,8 +65,8 @@ type KupmiosEnv =
   , ogmiosRequestSemaphore :: Maybe (Queue Unit)
   }
 
-initOgmiosRequestSemaphore :: Int -> Aff (Queue Unit)
-initOgmiosRequestSemaphore maxParallelRequests = do
+initOgmiosRequestSemaphore :: { maxParallelRequests :: Int } -> Aff (Queue Unit)
+initOgmiosRequestSemaphore { maxParallelRequests } = do
   sem <- Queue.new
   traverse_ (const (Queue.write sem unit)) $ 1 .. maxParallelRequests
   pure sem

From 22044b695b6d3e43724c01ed5f255ece33dc4744 Mon Sep 17 00:00:00 2001
From: Dzmitry Shuiski <errfrom@yandex.ru>
Date: Fri, 7 Nov 2025 17:19:03 +0100
Subject: [PATCH 4/5] Ogmios request semaphore: Switch to BoundedQueue; Add
 cooldown if empty

---
 src/Kupmios/KupmiosM.purs        | 31 ++++++++++++++++++++-----------
 src/Kupmios/KupmiosM/Kupo.purs   |  4 ++--
 src/Kupmios/KupmiosM/Ogmios.purs | 21 +++++++++++++++++----
 3 files changed, 39 insertions(+), 17 deletions(-)

diff --git a/src/Kupmios/KupmiosM.purs b/src/Kupmios/KupmiosM.purs
index d753ec3..622abf2 100644
--- a/src/Kupmios/KupmiosM.purs
+++ b/src/Kupmios/KupmiosM.purs
@@ -1,11 +1,12 @@
 -- | Kupo+Ogmios query layer monad.
 -- | This module defines an Aff interface for backend queries.
 module Cardano.Kupmios.KupmiosM
-  ( KupmiosM
-  , KupmiosEnv
+  ( KupmiosEnv
   , KupmiosConfig
-  , ParKupmiosM
+  , KupmiosM
   , KupmiosMT(KupmiosMT)
+  , ParKupmiosM
+  , Semaphore
   , handleAffjaxResponse
   , initOgmiosRequestSemaphore
   ) where
@@ -21,8 +22,8 @@ import Cardano.Provider.Error
   , ServiceError(ServiceOtherError)
   )
 import Cardano.Provider.ServerConfig (ServerConfig)
-import Concurrent.Queue (Queue)
-import Concurrent.Queue (new, write) as Queue
+import Concurrent.BoundedQueue (BoundedQueue)
+import Concurrent.BoundedQueue (new, write) as BoundedQueue
 import Control.Alt (class Alt)
 import Control.Alternative (class Alternative)
 import Control.Monad.Error.Class (class MonadError, class MonadThrow)
@@ -38,6 +39,7 @@ import Data.Log.Level (LogLevel)
 import Data.Log.Message (Message)
 import Data.Maybe (Maybe, fromMaybe)
 import Data.Newtype (class Newtype, unwrap, wrap)
+import Data.Time.Duration (Milliseconds)
 import Data.Traversable (traverse_)
 import Effect.Aff (Aff, ParAff)
 import Effect.Aff.Class (class MonadAff, liftAff)
@@ -52,8 +54,13 @@ import Effect.Exception (Error)
 -- | - logging level
 -- | - optional custom logger
 type KupmiosConfig =
-  { ogmiosConfig :: ServerConfig
-  , kupoConfig :: ServerConfig
+  { ogmios ::
+      { serverConfig :: ServerConfig
+      , requestSemaphoreCooldown :: Maybe Milliseconds
+      }
+  , kupo ::
+      { serverConfig :: ServerConfig
+      }
   , logLevel :: LogLevel
   , customLogger :: Maybe (LogLevel -> Message -> Aff Unit)
   , suppressLogs :: Boolean
@@ -62,13 +69,15 @@ type KupmiosConfig =
 -- | `KupmiosEnv` contains everything needed for `KupmiosM` to run.
 type KupmiosEnv =
   { config :: KupmiosConfig
-  , ogmiosRequestSemaphore :: Maybe (Queue Unit)
+  , ogmiosRequestSemaphore :: Maybe Semaphore
   }
 
-initOgmiosRequestSemaphore :: { maxParallelRequests :: Int } -> Aff (Queue Unit)
+type Semaphore = BoundedQueue Unit
+
+initOgmiosRequestSemaphore :: { maxParallelRequests :: Int } -> Aff Semaphore
 initOgmiosRequestSemaphore { maxParallelRequests } = do
-  sem <- Queue.new
-  traverse_ (const (Queue.write sem unit)) $ 1 .. maxParallelRequests
+  sem <- BoundedQueue.new maxParallelRequests
+  traverse_ (const (BoundedQueue.write sem unit)) $ 1 .. maxParallelRequests
   pure sem
 
 type KupmiosM = KupmiosMT Aff
diff --git a/src/Kupmios/KupmiosM/Kupo.purs b/src/Kupmios/KupmiosM/Kupo.purs
index 76fb09d..3d5049d 100644
--- a/src/Kupmios/KupmiosM/Kupo.purs
+++ b/src/Kupmios/KupmiosM/Kupo.purs
@@ -156,7 +156,7 @@ getScriptByHash scriptHash = do
 -- https://github.com/Plutonomicon/cardano-transaction-lib/issues/1293
 isTxConfirmed :: TransactionHash -> KupmiosM (Either ClientError (Maybe Slot))
 isTxConfirmed txHash = do
-  config <- asks (_.kupoConfig <<< _.config)
+  config <- asks (_.serverConfig <<< _.kupo <<< _.config)
   do
     -- we don't add `?unspent`, because we only care about existence of UTxOs,
     -- possibly they can be consumed
@@ -493,7 +493,7 @@ unwrapKupoAuxData (KupoAuxiliaryData mAuxData) = mAuxData
 kupoGetRequest
   :: String -> KupmiosM (Either Affjax.Error (Affjax.Response String))
 kupoGetRequest endpoint = do
-  config <- asks (_.kupoConfig <<< _.config)
+  config <- asks (_.serverConfig <<< _.kupo <<< _.config)
   logTrace' $ "sending kupo request: " <> endpoint
   liftAff $ kupoGetRequestAff config endpoint
 
diff --git a/src/Kupmios/KupmiosM/Ogmios.purs b/src/Kupmios/KupmiosM/Ogmios.purs
index 02a69fc..90591f5 100644
--- a/src/Kupmios/KupmiosM/Ogmios.purs
+++ b/src/Kupmios/KupmiosM/Ogmios.purs
@@ -46,7 +46,7 @@ import Cardano.Provider.ServerConfig (ServerConfig, mkHttpUrl)
 import Cardano.Types.CborBytes (CborBytes)
 import Cardano.Types.Chain as Chain
 import Cardano.Types.TransactionHash (TransactionHash)
-import Concurrent.Queue (read, write) as Queue
+import Concurrent.BoundedQueue (isEmpty, read, write) as BoundedQueue
 import Control.Monad.Error.Class (class MonadThrow, throwError)
 import Control.Monad.Reader.Class (ask)
 import Data.ByteArray (byteArrayToHex)
@@ -160,13 +160,26 @@ ogmiosPostRequest
   :: Aeson -- ^ JSON-RPC request body
   -> KupmiosM (Either Affjax.Error (Affjax.Response String))
 ogmiosPostRequest body = do
-  { config: { ogmiosConfig }, ogmiosRequestSemaphore } <- ask
+  { config: { ogmios }, ogmiosRequestSemaphore } <- ask
   logTrace' $ "sending ogmios HTTP request: " <> show body
-  let request = ogmiosPostRequestAff ogmiosConfig body
+  let request = ogmiosPostRequestAff ogmios.serverConfig body
   resp <-
     liftAff case ogmiosRequestSemaphore of
       Just sem ->
-        bracket (Queue.read sem) (const (Queue.write sem unit)) $ const request
+        let
+          acquireSem =
+            case ogmios.requestSemaphoreCooldown of
+              Nothing ->
+                BoundedQueue.read sem
+              Just cd ->
+                BoundedQueue.isEmpty sem >>=
+                  case _ of
+                    false ->
+                      BoundedQueue.read sem
+                    true ->
+                      delay cd *> BoundedQueue.read sem
+        in
+          bracket acquireSem (const (BoundedQueue.write sem unit)) $ const request
       Nothing ->
         request
   logTrace' $ "response: " <> (show $ hush resp)

From 19e1f1067c91ebfcd3323c32e88676ebf1f49ceb Mon Sep 17 00:00:00 2001
From: Dzmitry Shuiski <errfrom@yandex.ru>
Date: Mon, 10 Nov 2025 17:11:37 +0100
Subject: [PATCH 5/5] Add a changelog entry

---
 CHANGELOG.md | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index c229a70..ac776e0 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,18 @@ All notable changes to this project will be documented in this file.
 
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/) and we follow [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+# v3.0.0
+
+## Changed
+
+- `KupmiosConfig` and `KupmiosEnv` types. Ogmios cannot handle a high number of
+parallel HTTP requests, so we now limit concurrency using a semaphore managed
+within `KupmiosEnv`. The semaphore can be initialized with
+`initOgmiosRequestSemaphore`. Additionally, users can configure
+`requestSemaphoreCooldown` in `KupmiosConfig` to further throttle requests that
+exceed the semaphore limit. Note that this solution is intended as a temporary
+workaround, so contributions are more than welcome.
+
 # v2.1.0
 
 ## Changed