diff --git a/CHANGELOG.md b/CHANGELOG.md
index 09e725cf4e..931b6b2a16 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -9,6 +9,7 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 
  - #3558, Add the `admin-server-host` config to set the host for the admin server - @develop7
  - #3607, Log to stderr when the JWT secret is less than 32 characters long - @laurenceisla
+ - #2858, Performance improvements when calling RPCs via GET using indexes in more cases - @wolfgangwalther
 
 ### Fixed
 
diff --git a/src/PostgREST/Plan.hs b/src/PostgREST/Plan.hs
index 4acedf4264..4718b05ed0 100644
--- a/src/PostgREST/Plan.hs
+++ b/src/PostgREST/Plan.hs
@@ -25,7 +25,6 @@ module PostgREST.Plan
   , CallReadPlan(..)
   ) where
 
-import qualified Data.ByteString.Lazy          as LBS
 import qualified Data.HashMap.Strict           as HM
 import qualified Data.HashMap.Strict.InsOrd    as HMI
 import qualified Data.List                     as L
@@ -176,9 +175,9 @@ callReadPlan identifier conf sCache apiRequest@ApiRequest{iPreferences=Preferenc
   let relIdentifier = QualifiedIdentifier pdSchema (fromMaybe pdName $ Routine.funcTableName proc) -- done so a set returning function can embed other relations
   rPlan <- readPlan relIdentifier conf sCache apiRequest
   let args = case (invMethod, iContentMediaType) of
-        (InvRead _, _)      -> jsonRpcParams proc qsParams'
-        (Inv, MTUrlEncoded) -> maybe mempty (jsonRpcParams proc . payArray) iPayload
-        (Inv, _)            -> maybe mempty payRaw iPayload
+        (InvRead _, _)      -> DirectArgs $ toRpcParams proc qsParams'
+        (Inv, MTUrlEncoded) -> DirectArgs $ maybe mempty (toRpcParams proc . payArray) iPayload
+        (Inv, _)            -> JsonArgs $ payRaw <$> iPayload
       txMode = case (invMethod, pdVolatility) of
           (InvRead _,  _)          -> SQL.Read
           (Inv, Routine.Stable)    -> SQL.Read
@@ -955,11 +954,11 @@ resolveOrError ctx (Just table) field =
     CoercibleField{cfIRType=""} -> Left $ ColumnNotFound (tableName table) field
     cf                          -> Right $ withJsonParse ctx cf
 
-callPlan :: Routine -> ApiRequest -> S.Set FieldName -> LBS.ByteString -> ReadPlanTree -> CallPlan
+callPlan :: Routine -> ApiRequest -> S.Set FieldName -> CallArgs -> ReadPlanTree -> CallPlan
 callPlan proc ApiRequest{iPreferences=Preferences{..}} paramKeys args readReq = FunctionCall {
   funCQi = QualifiedIdentifier (pdSchema proc) (pdName proc)
 , funCParams = callParams
-, funCArgs = Just args
+, funCArgs = args
 , funCScalar = funcReturnsScalar proc
 , funCSetOfScalar = funcReturnsSetOfScalar proc
 , funCRetCompositeAlias = funcReturnsCompositeAlias proc
diff --git a/src/PostgREST/Plan/CallPlan.hs b/src/PostgREST/Plan/CallPlan.hs
index 76e3341f6b..32ef34c359 100644
--- a/src/PostgREST/Plan/CallPlan.hs
+++ b/src/PostgREST/Plan/CallPlan.hs
@@ -2,7 +2,9 @@
 module PostgREST.Plan.CallPlan
   ( CallPlan(..)
   , CallParams(..)
-  , jsonRpcParams
+  , CallArgs(..)
+  , RpcParamValue(..)
+  , toRpcParams
   )
 where
 
@@ -19,7 +21,7 @@ import Protolude
 data CallPlan = FunctionCall
   { funCQi                :: QualifiedIdentifier
   , funCParams            :: CallParams
-  , funCArgs              :: Maybe LBS.ByteString
+  , funCArgs              :: CallArgs
   , funCScalar            :: Bool
   , funCSetOfScalar       :: Bool
   , funCRetCompositeAlias :: Bool
@@ -30,14 +32,26 @@ data CallParams
   = KeyParams [RoutineParam] -- ^ Call with key params: func(a := val1, b:= val2)
   | OnePosParam RoutineParam -- ^ Call with positional params(only one supported): func(val)
 
+data CallArgs
+  = DirectArgs (HM.HashMap Text RpcParamValue)
+  | JsonArgs (Maybe LBS.ByteString)
+
+-- | RPC query param value `/rpc/func?v=<value>`, used for VARIADIC functions on form-urlencoded POST and GETs
+-- | It can be fixed `?v=1` or repeated `?v=1&v=2&v=3.
+data RpcParamValue = Fixed Text | Variadic [Text]
+instance JSON.ToJSON RpcParamValue where
+  toJSON (Fixed    v) = JSON.toJSON v
+  -- Not possible to get here anymore. Variadic arguments are only supported for
+  -- true variadic arguments, but the toJSON instance is only used for the "single unnamed json argument" case.
+  toJSON (Variadic v) = JSON.toJSON v
+
 -- | Convert rpc params `/rpc/func?a=val1&b=val2` to json `{"a": "val1", "b": "val2"}
-jsonRpcParams :: Routine -> [(Text, Text)] -> LBS.ByteString
-jsonRpcParams proc prms =
-  if not $ pdHasVariadic proc then -- if proc has no variadic param, save steps and directly convert to json
-    JSON.encode $ HM.fromList $ second JSON.toJSON <$> prms
+toRpcParams :: Routine -> [(Text, Text)] -> HM.HashMap Text RpcParamValue
+toRpcParams proc prms =
+  if not $ pdHasVariadic proc then -- if proc has no variadic param, save steps and directly convert to map
+    HM.fromList $ second Fixed <$> prms
   else
-    let paramsMap = HM.fromListWith mergeParams $ toRpcParamValue proc <$> prms in
-    JSON.encode paramsMap
+    HM.fromListWith mergeParams $ toRpcParamValue proc <$> prms
   where
     mergeParams :: RpcParamValue -> RpcParamValue -> RpcParamValue
     mergeParams (Variadic a) (Variadic b) = Variadic $ b ++ a
@@ -48,10 +62,3 @@ toRpcParamValue proc (k, v) | prmIsVariadic k = (k, Variadic [v])
                             | otherwise       = (k, Fixed v)
   where
     prmIsVariadic prm = isJust $ find (\RoutineParam{ppName, ppVar} -> ppName == prm && ppVar) $ pdParams proc
-
--- | RPC query param value `/rpc/func?v=<value>`, used for VARIADIC functions on form-urlencoded POST and GETs
--- | It can be fixed `?v=1` or repeated `?v=1&v=2&v=3.
-data RpcParamValue = Fixed Text | Variadic [Text]
-instance JSON.ToJSON RpcParamValue where
-  toJSON (Fixed    v) = JSON.toJSON v
-  toJSON (Variadic v) = JSON.toJSON v
diff --git a/src/PostgREST/Query/QueryBuilder.hs b/src/PostgREST/Query/QueryBuilder.hs
index 1729f0dce4..dc96b4fef9 100644
--- a/src/PostgREST/Query/QueryBuilder.hs
+++ b/src/PostgREST/Query/QueryBuilder.hs
@@ -1,5 +1,6 @@
 {-# LANGUAGE DuplicateRecordFields #-}
 {-# LANGUAGE NamedFieldPuns        #-}
+{-# LANGUAGE RecordWildCards       #-}
 {-|
 Module      : PostgREST.Query.QueryBuilder
 Description : PostgREST SQL queries generating functions.
@@ -16,8 +17,11 @@ module PostgREST.Query.QueryBuilder
   , limitedQuery
   ) where
 
+import qualified Data.Aeson                      as JSON
 import qualified Data.ByteString.Char8           as BS
+import qualified Data.HashMap.Strict             as HM
 import qualified Hasql.DynamicStatements.Snippet as SQL
+import qualified Hasql.Encoders                  as HE
 
 import Data.Maybe (fromJust)
 import Data.Tree  (Tree (..))
@@ -190,14 +194,19 @@ mutatePlanToQuery (Delete mainQi logicForest range ordts returnings)
     (whereRangeIdF, rangeIdF) = mutRangeF mainQi (cfName . coField <$> ordts)
 
 callPlanToQuery :: CallPlan -> PgVersion -> SQL.Snippet
-callPlanToQuery (FunctionCall qi params args returnsScalar returnsSetOfScalar returnsCompositeAlias returnings) pgVer =
+callPlanToQuery (FunctionCall qi params arguments returnsScalar returnsSetOfScalar returnsCompositeAlias returnings) pgVer =
   "SELECT " <> (if returnsScalar || returnsSetOfScalar then "pgrst_call.pgrst_scalar" else returnedColumns) <> " " <>
   fromCall
   where
+    jsonArgs = case arguments of
+      DirectArgs args -> Just $ JSON.encode args
+      JsonArgs json   -> json
     fromCall = case params of
-      OnePosParam prm -> "FROM " <> callIt (singleParameter args $ encodeUtf8 $ ppType prm)
+      OnePosParam prm -> "FROM " <> callIt (singleParameter jsonArgs $ encodeUtf8 $ ppType prm)
       KeyParams []    -> "FROM " <> callIt mempty
-      KeyParams prms  -> fromJsonBodyF args ((\p -> CoercibleField (ppName p) mempty False (ppTypeMaxLength p) Nothing Nothing) <$> prms) False True False <> ", " <>
+      KeyParams prms  -> case arguments of
+        DirectArgs args -> "FROM " <> callIt (fmtArgs prms args)
+        JsonArgs json   -> fromJsonBodyF json ((\p -> CoercibleField (ppName p) mempty False (ppTypeMaxLength p) Nothing Nothing) <$> prms) False True False <> ", " <>
                          "LATERAL " <> callIt (fmtParams prms)
 
     callIt :: SQL.Snippet -> SQL.Snippet
@@ -209,6 +218,23 @@ callPlanToQuery (FunctionCall qi params args returnsScalar returnsSetOfScalar re
     fmtParams prms = intercalateSnippet ", "
       ((\a -> (if ppVar a then "VARIADIC " else mempty) <> pgFmtIdent (ppName a) <> " := pgrst_body." <> pgFmtIdent (ppName a)) <$> prms)
 
+    fmtArgs :: [RoutineParam] -> HM.HashMap Text RpcParamValue -> SQL.Snippet
+    fmtArgs prms args = intercalateSnippet ", " $ fmtArg <$> prms
+      where
+        fmtArg RoutineParam{..} =
+          (if ppVar then "VARIADIC " else mempty) <>
+          pgFmtIdent ppName <>
+          " := " <>
+          encodeArg (HM.lookup ppName args) <>
+          "::" <>
+          SQL.sql (encodeUtf8 ppTypeMaxLength)
+        encodeArg :: Maybe RpcParamValue -> SQL.Snippet
+        encodeArg (Just (Variadic v)) = SQL.encoderAndParam (HE.nonNullable $ HE.foldableArray $ HE.nonNullable HE.text) v
+        encodeArg (Just (Fixed v)) = SQL.encoderAndParam (HE.nonNullable HE.unknown) $ encodeUtf8 v
+        -- Currently not supported: Calling functions without some of their arguments without DEFAULT.
+        -- We could fallback to providing this NULL value in those cases.
+        encodeArg Nothing = "NULL"
+
     returnedColumns :: SQL.Snippet
     returnedColumns
       | null returnings = "*"
diff --git a/test/spec/Feature/Query/PlanSpec.hs b/test/spec/Feature/Query/PlanSpec.hs
index 182ac99a55..f1e27b1178 100644
--- a/test/spec/Feature/Query/PlanSpec.hs
+++ b/test/spec/Feature/Query/PlanSpec.hs
@@ -348,7 +348,7 @@ spec actualPgVersion = do
       r <- request methodGet "/rpc/get_projects_below?id=3"
              [planHdr] ""
 
-      liftIO $ planCost r `shouldSatisfy` (< 45.4)
+      liftIO $ planCost r `shouldSatisfy` (< 35.4)
 
     it "should not exceed cost when calling setof composite proc with empty params" $ do
       r <- request methodGet "/rpc/getallprojects"
@@ -360,7 +360,7 @@ spec actualPgVersion = do
       r <- request methodGet "/rpc/add_them?a=3&b=4"
              [planHdr] ""
 
-      liftIO $ planCost r `shouldSatisfy` (< 0.11)
+      liftIO $ planCost r `shouldSatisfy` (< 0.08)
 
     context "function inlining" $ do
       it "should inline a zero argument function(the function won't appear in the plan tree)" $ do