diff --git a/Cargo.lock b/Cargo.lock
index b29be2bbc4..0e07909f40 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -3128,6 +3128,20 @@ dependencies = [
  "winapi",
 ]
 
+[[package]]
+name = "num"
+version = "0.4.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "35bd024e8b2ff75562e5f34e7f4905839deb4b22955ef5e73d2fea1b9813cb23"
+dependencies = [
+ "num-bigint",
+ "num-complex",
+ "num-integer",
+ "num-iter",
+ "num-rational",
+ "num-traits",
+]
+
 [[package]]
 name = "num-bigint"
 version = "0.4.5"
@@ -3138,6 +3152,15 @@ dependencies = [
  "num-traits",
 ]
 
+[[package]]
+name = "num-complex"
+version = "0.4.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "73f88a1307638156682bada9d7604135552957b7818057dcef22705b4d509495"
+dependencies = [
+ "num-traits",
+]
+
 [[package]]
 name = "num-conv"
 version = "0.1.0"
@@ -3153,6 +3176,28 @@ dependencies = [
  "num-traits",
 ]
 
+[[package]]
+name = "num-iter"
+version = "0.1.45"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1429034a0490724d0075ebb2bc9e875d6503c3cf69e235a8941aa757d83ef5bf"
+dependencies = [
+ "autocfg",
+ "num-integer",
+ "num-traits",
+]
+
+[[package]]
+name = "num-rational"
+version = "0.4.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f83d14da390562dca69fc84082e73e548e1ad308d24accdedd2720017cb37824"
+dependencies = [
+ "num-bigint",
+ "num-integer",
+ "num-traits",
+]
+
 [[package]]
 name = "num-traits"
 version = "0.2.19"
@@ -5116,6 +5161,7 @@ dependencies = [
  "mime",
  "moka",
  "nom",
+ "num",
  "num_cpus",
  "once_cell",
  "opentelemetry 0.23.0",
diff --git a/Cargo.toml b/Cargo.toml
index 3a5fc97694..5bffcadf33 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -159,6 +159,7 @@ tokio-test = "0.4.4"
 base64 = "0.22.1"
 tailcall-hasher = { path = "tailcall-hasher" }
 serde_json_borrow = "0.5.0"
+num = "0.4.3"
 
 [dev-dependencies]
 tailcall-prettier = { path = "tailcall-prettier" }
diff --git a/src/core/counter.rs b/src/core/counter.rs
index afb7b2c138..5474e90300 100644
--- a/src/core/counter.rs
+++ b/src/core/counter.rs
@@ -1,15 +1,38 @@
 use std::cell::Cell;
+use std::sync::Mutex;
+
+pub trait Count {
+    type Item;
+    fn next(&self) -> Self::Item;
+}
 
-#[allow(unused)]
 #[derive(Default)]
-pub struct Counter(Cell<usize>);
-impl Counter {
-    pub fn new(start: usize) -> Self {
+pub struct Counter<A>(Cell<A>);
+impl<A> Counter<A> {
+    pub fn new(start: A) -> Self {
         Self(Cell::new(start))
     }
-    pub fn next(&self) -> usize {
+}
+
+impl<A: Copy + num::Num> Count for Counter<A> {
+    type Item = A;
+
+    fn next(&self) -> A {
         let curr = self.0.get();
-        self.0.set(curr + 1);
+        self.0.set(curr + A::one());
         curr
     }
 }
+
+#[derive(Default)]
+pub struct AtomicCounter<A>(Mutex<A>);
+
+impl<A: Copy + num::Num> Count for AtomicCounter<A> {
+    type Item = A;
+
+    fn next(&self) -> A {
+        let mut x = self.0.lock().unwrap();
+        *x = *x + A::one();
+        *x
+    }
+}
diff --git a/src/core/generator/json/mod.rs b/src/core/generator/json/mod.rs
index a67776fe3b..bde44f982c 100644
--- a/src/core/generator/json/mod.rs
+++ b/src/core/generator/json/mod.rs
@@ -10,10 +10,10 @@ pub use query_generator::QueryGenerator;
 pub use schema_generator::SchemaGenerator;
 pub use types_generator::TypesGenerator;
 
-use crate::core::counter::Counter;
+use crate::core::counter::{Count, Counter};
 
 pub struct NameGenerator {
-    counter: Counter,
+    counter: Counter<usize>,
     prefix: String,
 }
 
diff --git a/src/core/ir/jit/builder.rs b/src/core/ir/jit/builder.rs
index 8f05b4831b..9adca712f3 100644
--- a/src/core/ir/jit/builder.rs
+++ b/src/core/ir/jit/builder.rs
@@ -6,14 +6,14 @@ use async_graphql_parser::types::{OperationType, SelectionSet};
 use super::field_index::{FieldIndex, QueryField};
 use super::model::*;
 use crate::core::blueprint::Blueprint;
-use crate::core::counter::Counter;
+use crate::core::counter::{Count, Counter};
 use crate::core::merge_right::MergeRight;
 
 #[allow(unused)]
 pub struct ExecutionPlanBuilder {
     pub index: FieldIndex,
-    pub arg_id: Counter,
-    pub field_id: Counter,
+    pub arg_id: Counter<usize>,
+    pub field_id: Counter<usize>,
     pub document: ExecutableDocument,
 }
 
diff --git a/src/core/ir/jit/context.rs b/src/core/ir/jit/context.rs
index f32a4703b9..1d8beebbf5 100644
--- a/src/core/ir/jit/context.rs
+++ b/src/core/ir/jit/context.rs
@@ -5,12 +5,12 @@ use serde_json_borrow::OwnedValue;
 
 use super::model::{ExecutionPlan, Field, FieldId, Parent};
 use super::store::Store;
-use crate::core::ir::{EvaluationError, IoId, IR};
+use crate::core::ir::{CallId, EvaluationError, IR};
 
 #[allow(unused)]
 pub struct ExecutionContext {
     plan: ExecutionPlan,
-    store: Mutex<Store<IoId, OwnedValue>>,
+    store: Mutex<Store<CallId, OwnedValue>>,
 }
 
 #[allow(unused)]
@@ -67,7 +67,7 @@ impl ExecutionContext {
             .collect::<Vec<_>>()
     }
 
-    pub async fn execute(self) -> Result<Store<IoId, OwnedValue>, EvaluationError> {
+    pub async fn execute(self) -> Result<Store<CallId, OwnedValue>, EvaluationError> {
         future::join_all(
             self.root()
                 .iter()
diff --git a/src/core/ir/jit/snapshots/tailcall__core__ir__jit__builder__tests__default_value.snap b/src/core/ir/jit/snapshots/tailcall__core__ir__jit__builder__tests__default_value.snap
index 8f0379be4a..102f565a68 100644
--- a/src/core/ir/jit/snapshots/tailcall__core__ir__jit__builder__tests__default_value.snap
+++ b/src/core/ir/jit/snapshots/tailcall__core__ir__jit__builder__tests__default_value.snap
@@ -3,7 +3,7 @@ source: src/core/ir/jit/builder.rs
 expression: plan
 ---
 ExecutionPlan {
-    fields: [
+    parent: [
         Field {
             id: 0,
             name: "createPost",
@@ -48,7 +48,7 @@ ExecutionPlan {
             ),
         },
     ],
-    field_children: [
+    children: [
         Field {
             id: 0,
             name: "createPost",
diff --git a/src/core/ir/jit/snapshots/tailcall__core__ir__jit__builder__tests__fragments.snap b/src/core/ir/jit/snapshots/tailcall__core__ir__jit__builder__tests__fragments.snap
index 0d5df6472b..ce618841ee 100644
--- a/src/core/ir/jit/snapshots/tailcall__core__ir__jit__builder__tests__fragments.snap
+++ b/src/core/ir/jit/snapshots/tailcall__core__ir__jit__builder__tests__fragments.snap
@@ -3,7 +3,7 @@ source: src/core/ir/jit/builder.rs
 expression: plan
 ---
 ExecutionPlan {
-    fields: [
+    parent: [
         Field {
             id: 0,
             name: "name",
@@ -39,7 +39,7 @@ ExecutionPlan {
             ],
         },
     ],
-    field_children: [
+    children: [
         Field {
             id: 0,
             name: "name",
diff --git a/src/core/ir/jit/snapshots/tailcall__core__ir__jit__builder__tests__from_document.snap b/src/core/ir/jit/snapshots/tailcall__core__ir__jit__builder__tests__from_document.snap
index 13663a037e..f4cd66f7ea 100644
--- a/src/core/ir/jit/snapshots/tailcall__core__ir__jit__builder__tests__from_document.snap
+++ b/src/core/ir/jit/snapshots/tailcall__core__ir__jit__builder__tests__from_document.snap
@@ -3,7 +3,7 @@ source: src/core/ir/jit/builder.rs
 expression: plan
 ---
 ExecutionPlan {
-    fields: [
+    parent: [
         Field {
             id: 0,
             name: "posts",
@@ -36,7 +36,7 @@ ExecutionPlan {
             ),
         },
     ],
-    field_children: [
+    children: [
         Field {
             id: 0,
             name: "posts",
diff --git a/src/core/ir/jit/snapshots/tailcall__core__ir__jit__builder__tests__multiple_operations.snap b/src/core/ir/jit/snapshots/tailcall__core__ir__jit__builder__tests__multiple_operations.snap
index 863d09bfb3..9f47fa7dbf 100644
--- a/src/core/ir/jit/snapshots/tailcall__core__ir__jit__builder__tests__multiple_operations.snap
+++ b/src/core/ir/jit/snapshots/tailcall__core__ir__jit__builder__tests__multiple_operations.snap
@@ -3,7 +3,7 @@ source: src/core/ir/jit/builder.rs
 expression: plan
 ---
 ExecutionPlan {
-    fields: [
+    parent: [
         Field {
             id: 0,
             name: "user",
@@ -62,7 +62,7 @@ ExecutionPlan {
             ),
         },
     ],
-    field_children: [
+    children: [
         Field {
             id: 0,
             name: "user",
diff --git a/src/core/ir/jit/snapshots/tailcall__core__ir__jit__builder__tests__simple_mutation.snap b/src/core/ir/jit/snapshots/tailcall__core__ir__jit__builder__tests__simple_mutation.snap
index 446fe4dd67..bfa496f510 100644
--- a/src/core/ir/jit/snapshots/tailcall__core__ir__jit__builder__tests__simple_mutation.snap
+++ b/src/core/ir/jit/snapshots/tailcall__core__ir__jit__builder__tests__simple_mutation.snap
@@ -3,7 +3,7 @@ source: src/core/ir/jit/builder.rs
 expression: plan
 ---
 ExecutionPlan {
-    fields: [
+    parent: [
         Field {
             id: 0,
             name: "createUser",
@@ -103,7 +103,7 @@ ExecutionPlan {
             ),
         },
     ],
-    field_children: [
+    children: [
         Field {
             id: 0,
             name: "createUser",
diff --git a/src/core/ir/jit/snapshots/tailcall__core__ir__jit__builder__tests__simple_query.snap b/src/core/ir/jit/snapshots/tailcall__core__ir__jit__builder__tests__simple_query.snap
index 057fe0f27f..8909f45e90 100644
--- a/src/core/ir/jit/snapshots/tailcall__core__ir__jit__builder__tests__simple_query.snap
+++ b/src/core/ir/jit/snapshots/tailcall__core__ir__jit__builder__tests__simple_query.snap
@@ -3,7 +3,7 @@ source: src/core/ir/jit/builder.rs
 expression: plan
 ---
 ExecutionPlan {
-    fields: [
+    parent: [
         Field {
             id: 0,
             name: "posts",
@@ -28,7 +28,7 @@ ExecutionPlan {
             ),
         },
     ],
-    field_children: [
+    children: [
         Field {
             id: 0,
             name: "posts",
diff --git a/src/core/ir/jit/snapshots/tailcall__core__ir__jit__builder__tests__unions.snap b/src/core/ir/jit/snapshots/tailcall__core__ir__jit__builder__tests__unions.snap
index 2232a7cfa8..927b6fe3f2 100644
--- a/src/core/ir/jit/snapshots/tailcall__core__ir__jit__builder__tests__unions.snap
+++ b/src/core/ir/jit/snapshots/tailcall__core__ir__jit__builder__tests__unions.snap
@@ -3,7 +3,7 @@ source: src/core/ir/jit/builder.rs
 expression: plan
 ---
 ExecutionPlan {
-    fields: [
+    parent: [
         Field {
             id: 0,
             name: "getUserIdOrEmail",
@@ -24,7 +24,7 @@ ExecutionPlan {
             ],
         },
     ],
-    field_children: [
+    children: [
         Field {
             id: 0,
             name: "getUserIdOrEmail",
diff --git a/src/core/ir/jit/snapshots/tailcall__core__ir__jit__builder__tests__variables.snap b/src/core/ir/jit/snapshots/tailcall__core__ir__jit__builder__tests__variables.snap
index 079c8349c5..340f673c8b 100644
--- a/src/core/ir/jit/snapshots/tailcall__core__ir__jit__builder__tests__variables.snap
+++ b/src/core/ir/jit/snapshots/tailcall__core__ir__jit__builder__tests__variables.snap
@@ -3,7 +3,7 @@ source: src/core/ir/jit/builder.rs
 expression: plan
 ---
 ExecutionPlan {
-    fields: [
+    parent: [
         Field {
             id: 0,
             name: "user",
@@ -42,7 +42,7 @@ ExecutionPlan {
             ),
         },
     ],
-    field_children: [
+    children: [
         Field {
             id: 0,
             name: "user",
diff --git a/src/core/ir/jit/synth.rs b/src/core/ir/jit/synth.rs
index b6fba5f7c5..e823af8e30 100644
--- a/src/core/ir/jit/synth.rs
+++ b/src/core/ir/jit/synth.rs
@@ -2,22 +2,22 @@ pub use serde_json_borrow::*;
 
 use super::model::{Children, Field};
 use super::store::{Data, Store};
-use crate::core::ir::IoId;
+use crate::core::ir::CallId;
 
 #[allow(unused)]
 pub struct Synth {
     operation: Field<Children>,
-    store: Store<IoId, OwnedValue>,
+    store: Store<CallId, OwnedValue>,
 }
 
 #[allow(unused)]
 impl Synth {
-    pub fn new(operation: Field<Children>, store: Store<IoId, OwnedValue>) -> Self {
+    pub fn new(operation: Field<Children>, store: Store<CallId, OwnedValue>) -> Self {
         Synth { operation, store }
     }
 
     pub fn synthesize(&self) -> Value<'_> {
-        let value = self.store.get(&IoId::new(0));
+        let value = self.store.get(&CallId::new(0));
         self.iter(&self.operation, value)
     }
 
@@ -28,7 +28,7 @@ impl Synth {
     pub fn iter<'a>(
         &'a self,
         node: &'a Field<Children>,
-        parent: Option<&'a Data<IoId, OwnedValue>>,
+        parent: Option<&'a Data<CallId, OwnedValue>>,
     ) -> Value<'a> {
         match parent {
             Some(parent) => match parent.data.as_ref().map(|v| v.get_value()) {
@@ -55,7 +55,7 @@ impl Synth {
         &'a self,
         node: &'a Field<Children>,
         parent: Option<&'a Value<'a>>,
-        value: &Data<IoId, OwnedValue>,
+        value: &Data<CallId, OwnedValue>,
     ) -> Value<'a> {
         match parent {
             Some(Value::Object(obj)) => {
@@ -117,7 +117,7 @@ mod tests {
     use crate::core::ir::jit::model::FieldId;
     use crate::core::ir::jit::store::{Data, Store};
     use crate::core::ir::jit::synth::Synth;
-    use crate::core::ir::IoId;
+    use crate::core::ir::CallId;
     use crate::core::valid::Validator;
 
     const POSTS: &str = r#"
@@ -148,7 +148,7 @@ mod tests {
 
     const CONFIG: &str = include_str!("./fixtures/jsonplaceholder-mutation.graphql");
 
-    fn synth(query: &str, data: Vec<(IoId, Data<IoId, OwnedValue>)>) -> String {
+    fn synth(query: &str, data: Vec<(CallId, Data<CallId, OwnedValue>)>) -> String {
         let config = Config::from_sdl(CONFIG).to_result().unwrap();
         let blueprint = Blueprint::try_from(&config.into()).unwrap();
         let document = async_graphql::parser::parse_query(query).unwrap();
@@ -172,18 +172,18 @@ mod tests {
         let store = vec![
             // Insert Root
             (
-                IoId::new(0),
+                CallId::new(0),
                 Data {
                     data: None,
-                    extras: HashMap::from_iter(vec![(FieldId::new(0), IoId::new(1))].into_iter()),
+                    extras: HashMap::from_iter(vec![(FieldId::new(0), CallId::new(1))].into_iter()),
                 },
             ),
             // Insert /posts
             (
-                IoId::new(1),
+                CallId::new(1),
                 Data {
                     data: Some(OwnedValue::from_str(POSTS).unwrap()),
-                    extras: HashMap::from_iter(vec![(FieldId::new(0), IoId::new(1))].into_iter()),
+                    extras: HashMap::from_iter(vec![(FieldId::new(0), CallId::new(1))].into_iter()),
                 },
             ),
         ];
@@ -205,18 +205,18 @@ mod tests {
         let store = vec![
             // Insert Root
             (
-                IoId::new(0),
+                CallId::new(0),
                 Data {
                     data: None,
-                    extras: HashMap::from_iter(vec![(FieldId::new(0), IoId::new(1))].into_iter()),
+                    extras: HashMap::from_iter(vec![(FieldId::new(0), CallId::new(1))].into_iter()),
                 },
             ),
             // Insert /users
             (
-                IoId::new(1),
+                CallId::new(1),
                 Data {
                     data: Some(OwnedValue::from_str(USERS).unwrap()),
-                    extras: HashMap::from_iter(vec![(FieldId::new(0), IoId::new(1))].into_iter()),
+                    extras: HashMap::from_iter(vec![(FieldId::new(0), CallId::new(1))].into_iter()),
                 },
             ),
         ];
@@ -237,15 +237,15 @@ mod tests {
         let store = vec![
             // Insert Root
             (
-                IoId::new(0),
+                CallId::new(0),
                 Data {
                     data: None,
-                    extras: HashMap::from_iter(vec![(FieldId::new(0), IoId::new(1))].into_iter()),
+                    extras: HashMap::from_iter(vec![(FieldId::new(0), CallId::new(1))].into_iter()),
                 },
             ),
             // Insert /user/:id
             (
-                IoId::new(1),
+                CallId::new(1),
                 Data {
                     data: Some(OwnedValue::from_str(USER).unwrap()),
                     extras: Default::default(),
@@ -269,23 +269,23 @@ mod tests {
         let store = vec![
             // Insert Root
             (
-                IoId::new(0),
+                CallId::new(0),
                 Data {
                     data: None,
-                    extras: HashMap::from_iter(vec![(FieldId::new(0), IoId::new(1))].into_iter()),
+                    extras: HashMap::from_iter(vec![(FieldId::new(0), CallId::new(1))].into_iter()),
                 },
             ),
             // Insert /posts/:id
             (
-                IoId::new(1),
+                CallId::new(1),
                 Data {
                     data: Some(OwnedValue::from_str(POST).unwrap()),
-                    extras: HashMap::from_iter(vec![(FieldId::new(3), IoId::new(2))].into_iter()),
+                    extras: HashMap::from_iter(vec![(FieldId::new(3), CallId::new(2))].into_iter()),
                 },
             ),
             // Insert /user/:id
             (
-                IoId::new(2),
+                CallId::new(2),
                 Data {
                     data: Some(OwnedValue::from_str(USER).unwrap()),
                     extras: Default::default(),
@@ -310,23 +310,23 @@ mod tests {
         let store = vec![
             // Insert Root
             (
-                IoId::new(0),
+                CallId::new(0),
                 Data {
                     data: None,
-                    extras: HashMap::from_iter(vec![(FieldId::new(0), IoId::new(1))].into_iter()),
+                    extras: HashMap::from_iter(vec![(FieldId::new(0), CallId::new(1))].into_iter()),
                 },
             ),
             // Insert /posts
             (
-                IoId::new(1),
+                CallId::new(1),
                 Data {
                     data: Some(OwnedValue::from_str(POSTS).unwrap()),
-                    extras: HashMap::from_iter(vec![(FieldId::new(3), IoId::new(2))].into_iter()),
+                    extras: HashMap::from_iter(vec![(FieldId::new(3), CallId::new(2))].into_iter()),
                 },
             ),
             // Insert /user/:id
             (
-                IoId::new(2),
+                CallId::new(2),
                 Data {
                     data: Some(OwnedValue::from_str(USER).unwrap()),
                     extras: Default::default(),
@@ -351,30 +351,30 @@ mod tests {
         let store = vec![
             // Insert Root
             (
-                IoId::new(0),
+                CallId::new(0),
                 Data {
                     data: None,
-                    extras: HashMap::from_iter(vec![(FieldId::new(0), IoId::new(1))].into_iter()),
+                    extras: HashMap::from_iter(vec![(FieldId::new(0), CallId::new(1))].into_iter()),
                 },
             ),
             // Insert /posts
             (
-                IoId::new(1),
+                CallId::new(1),
                 Data {
                     data: Some(OwnedValue::from_str(POSTS).unwrap()),
-                    extras: HashMap::from_iter(vec![(FieldId::new(2), IoId::new(2))].into_iter()),
+                    extras: HashMap::from_iter(vec![(FieldId::new(2), CallId::new(2))].into_iter()),
                 },
             ),
             // Insert /user/:id
             (
-                IoId::new(2),
+                CallId::new(2),
                 Data {
                     data: Some(OwnedValue::from_str(USER).unwrap()),
-                    extras: HashMap::from_iter(vec![(FieldId::new(4), IoId::new(3))].into_iter()),
+                    extras: HashMap::from_iter(vec![(FieldId::new(4), CallId::new(3))].into_iter()),
                 },
             ),
             (
-                IoId::new(3),
+                CallId::new(3),
                 Data {
                     data: Some(OwnedValue::from_str(TODO).unwrap()),
                     extras: Default::default(),
diff --git a/src/core/ir/mod.rs b/src/core/ir/mod.rs
index 5f202ea75b..00d0944d35 100644
--- a/src/core/ir/mod.rs
+++ b/src/core/ir/mod.rs
@@ -25,6 +25,15 @@ use crate::core::blueprint::DynamicValue;
 use crate::core::json::JsonLike;
 use crate::core::serde_value_ext::ValueExt;
 
+#[derive(Eq, Hash, PartialEq, Clone, Debug)]
+pub struct CallId(usize);
+
+impl CallId {
+    pub fn new(id: usize) -> Self {
+        Self(id)
+    }
+}
+
 #[derive(Clone, Debug)]
 pub enum IR {
     Context(Context),