diff --git a/libdd-trace-utils/src/change_buffer/mod.rs b/libdd-trace-utils/src/change_buffer/mod.rs
new file mode 100644
index 0000000000..02dbf3619c
--- /dev/null
+++ b/libdd-trace-utils/src/change_buffer/mod.rs
@@ -0,0 +1,351 @@
+use std::collections::HashMap;
+
+use anyhow::{anyhow, Result};
+
+mod utils;
+use utils::*;
+
+mod trace;
+use trace::*;
+
+use crate::span::{Span, SpanText};
+
+#[derive(Clone, Copy)]
+pub struct ChangeBuffer(*const u8);
+unsafe impl Send for ChangeBuffer {}
+unsafe impl Sync for ChangeBuffer {}
+
+impl std::ops::Deref for ChangeBuffer {
+    type Target = *const u8;
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+impl Default for ChangeBuffer {
+    fn default() -> Self {
+        ChangeBuffer(std::ptr::null_mut())
+    }
+}
+
+impl From<*const u8> for ChangeBuffer {
+    fn from(val: *const u8) -> Self {
+        Self(val)
+    }
+}
+
+#[derive(Default)]
+pub struct ChangeBufferState<T: SpanText + Clone> {
+    change_buffer: ChangeBuffer,
+    spans: HashMap<u64, Span<T>>,
+    traces: HashMap<u128, Trace<T>>,
+    string_table: HashMap<u32, T>,
+    trace_span_counts: HashMap<u128, usize>,
+    tracer_service: T,
+    tracer_language: T,
+    pid: f64,
+}
+
+fn new_span<T: SpanText>(span_id: u64, parent_id: u64, trace_id: u128) -> Span<T> {
+    Span {
+        span_id,
+        trace_id,
+        parent_id,
+        ..Default::default()
+    }
+}
+
+impl<T: SpanText + Clone> ChangeBufferState<T> {
+    pub fn new(
+        change_buffer: ChangeBuffer,
+        tracer_service: T,
+        tracer_language: T,
+        pid: f64,
+    ) -> Self {
+        ChangeBufferState {
+            change_buffer,
+            tracer_service,
+            tracer_language,
+            pid,
+            ..Default::default()
+        }
+    }
+
+    pub fn flush_chunk(
+        &mut self,
+        span_ids: Vec<u64>,
+        first_is_local_root: bool,
+    ) -> Result<Vec<Span<T>>> {
+        let mut chunk_trace_id: Option<u128> = None;
+        let mut is_local_root = first_is_local_root;
+        let mut is_chunk_root = true;
+
+        let spans_vec = span_ids
+            .iter()
+            .map(|span_id| -> Result<Span<T>> {
+                let maybe_span = self.spans.remove(span_id);
+
+                let mut span = maybe_span.ok_or_else(|| anyhow!("span not found: {}", span_id))?;
+                chunk_trace_id = Some(span.trace_id);
+
+                if is_local_root {
+                    self.copy_in_sampling_tags(&mut span);
+                    span.metrics
+                        .insert(T::from_static_str("_dd.top_level"), 1.0);
+                    is_local_root = false;
+                }
+                if is_chunk_root {
+                    self.copy_in_chunk_tags(&mut span);
+                    is_chunk_root = false;
+                }
+
+                self.process_one_span(&mut span);
+
+                Ok(span)
+            })
+            .collect::<Result<Vec<_>>>()?;
+
+        // Clean up trace if no spans remain for it
+        if let Some(trace_id) = chunk_trace_id {
+            if let Some(count) = self.trace_span_counts.get_mut(&trace_id) {
+                let len = span_ids.len();
+                if *count <= len {
+                    // All spans for this trace have been flushed
+                    self.traces.remove(&trace_id);
+                    self.trace_span_counts.remove(&trace_id);
+                } else {
+                    *count -= len;
+                }
+            }
+        }
+
+        Ok(spans_vec)
+    }
+
+    fn copy_in_sampling_tags(&self, span: &mut Span<T>) {
+        if let Some(trace) = self.traces.get(&span.trace_id) {
+            if let Some(rule) = trace.sampling_rule_decision {
+                span.metrics
+                    .insert(T::from_static_str("_dd.rule_psr"), rule);
+            }
+            if let Some(rule) = trace.sampling_limit_decision {
+                span.metrics.insert(T::from_static_str("_dd.;_psr"), rule);
+            }
+            if let Some(rule) = trace.sampling_agent_decision {
+                span.metrics
+                    .insert(T::from_static_str("_dd.agent_psr"), rule);
+            }
+        }
+    }
+
+    fn copy_in_chunk_tags(&self, span: &mut Span<T>) {
+        if let Some(trace) = self.traces.get(&span.trace_id) {
+            span.meta.reserve(trace.meta.len());
+            span.meta.extend(trace.meta.clone());
+            span.metrics.reserve(trace.metrics.len());
+            span.metrics.extend(trace.metrics.clone());
+        }
+    }
+
+    fn process_one_span(&self, span: &mut Span<T>) {
+        // TODO span.sample();
+
+        if let Some(kind) = span.meta.get("kind") {
+            if kind != &T::from_static_str("internal") {
+                span.metrics.insert(T::from_static_str("_dd.measured"), 1.0);
+            }
+        }
+
+        if span.service != self.tracer_service {
+            span.meta.insert(
+                T::from_static_str("_dd.base_service"),
+                self.tracer_service.clone(),
+            );
+            // TODO span.service should be added to the "extra services" used by RC, which is not
+            // yet implemented here
+        }
+
+        // SKIP setting single-span ingestion. They should be set when sampling is finalized for
+        // the span.
+
+        span.meta
+            .insert(T::from_static_str("language"), self.tracer_language.clone());
+        span.metrics
+            .insert(T::from_static_str("process_id"), self.pid);
+
+        if let Some(trace) = self.traces.get(&span.trace_id) {
+            if let Some(origin) = trace.origin.clone() {
+                span.meta.insert(T::from_static_str("_dd.origin"), origin);
+            }
+        }
+
+        // SKIP hostname. This can be an option to the span constructor, so we'll set the tag at
+        // that point.
+
+        // TODO Sampling priority, if we're not doing that ahead of time.
+    }
+
+    pub fn flush_change_buffer(&mut self) -> Result<()> {
+        let mut index = 0;
+        let buf = *self.change_buffer;
+        let mut count: u64 = get_num_raw(buf, &mut index);
+
+        while count > 0 {
+            let op = BufferedOperation::from_buf(&self.change_buffer, &mut index);
+            self.interpret_operation(&mut index, &op)?;
+            count -= 1;
+        }
+
+        // Write 0 back to the count position so the writing side of the buffer knows the queue was
+        // flushed
+        let buf_mut = buf as *mut u8;
+        unsafe {
+            std::ptr::copy_nonoverlapping([0u8; 8].as_ptr(), buf_mut, 8);
+        }
+
+        Ok(())
+    }
+
+    fn get_string_arg(&self, index: &mut usize) -> Result<T> {
+        let num: u32 = self.get_num_arg(index);
+        self.string_table
+            .get(&num)
+            .cloned()
+            .ok_or_else(|| anyhow!("string not found internally: {}", num))
+    }
+
+    fn get_num_arg<U: Copy + FromBytes>(&self, index: &mut usize) -> U {
+        get_num_raw(*self.change_buffer, index)
+    }
+
+    fn get_mut_span(&mut self, id: &u64) -> Result<&mut Span<T>> {
+        self.spans
+            .get_mut(id)
+            .ok_or_else(|| anyhow!("span not found internally: {}", id))
+    }
+
+    fn get_span(&self, id: &u64) -> Result<&Span<T>> {
+        self.spans
+            .get(id)
+            .ok_or_else(|| anyhow!("span not found internally: {}", id))
+    }
+
+    fn interpret_operation(&mut self, index: &mut usize, op: &BufferedOperation) -> Result<()> {
+        match op.opcode {
+            OpCode::Create => {
+                let trace_id: u128 = self.get_num_arg(index);
+                let parent_id = self.get_num_arg(index);
+                let span = new_span(op.span_id, parent_id, trace_id);
+                self.spans.insert(op.span_id, span);
+                // Ensure trace exists (creates new one if this is the first span for this trace)
+                self.traces.entry(trace_id).or_default();
+
+                *self.trace_span_counts.entry(trace_id).or_insert(0) += 1;
+            }
+            OpCode::SetMetaAttr => {
+                let name = self.get_string_arg(index)?;
+                let val = self.get_string_arg(index)?;
+                let span = self.get_mut_span(&op.span_id)?;
+                span.meta.insert(name, val);
+            }
+            OpCode::SetMetricAttr => {
+                let name = self.get_string_arg(index)?;
+                let val: f64 = self.get_num_arg(index);
+                let span = self.get_mut_span(&op.span_id)?;
+                span.metrics.insert(name, val);
+            }
+            OpCode::SetServiceName => {
+                self.get_mut_span(&op.span_id)?.service = self.get_string_arg(index)?;
+            }
+            OpCode::SetResourceName => {
+                self.get_mut_span(&op.span_id)?.resource = self.get_string_arg(index)?;
+            }
+            OpCode::SetError => {
+                self.get_mut_span(&op.span_id)?.error = self.get_num_arg(index);
+            }
+            OpCode::SetStart => {
+                self.get_mut_span(&op.span_id)?.start = self.get_num_arg(index);
+            }
+            OpCode::SetDuration => {
+                self.get_mut_span(&op.span_id)?.duration = self.get_num_arg(index);
+            }
+            OpCode::SetType => {
+                self.get_mut_span(&op.span_id)?.r#type = self.get_string_arg(index)?;
+            }
+            OpCode::SetName => {
+                self.get_mut_span(&op.span_id)?.name = self.get_string_arg(index)?;
+            }
+            OpCode::SetTraceMetaAttr => {
+                let name = self.get_string_arg(index)?;
+                let val = self.get_string_arg(index)?;
+                let trace_id = self.get_span(&op.span_id)?.trace_id;
+                if let Some(trace) = self.traces.get_mut(&trace_id) {
+                    trace.meta.insert(name, val);
+                }
+            }
+            OpCode::SetTraceMetricsAttr => {
+                let name = self.get_string_arg(index)?;
+                let val = self.get_num_arg(index);
+                let trace_id = self.get_span(&op.span_id)?.trace_id;
+                if let Some(trace) = self.traces.get_mut(&trace_id) {
+                    trace.metrics.insert(name, val);
+                }
+            }
+            OpCode::SetTraceOrigin => {
+                let origin = self.get_string_arg(index)?;
+                let trace_id = self.get_span(&op.span_id)?.trace_id;
+                if let Some(trace) = self.traces.get_mut(&trace_id) {
+                    trace.origin = Some(origin);
+                }
+            }
+        };
+
+        Ok(())
+    }
+
+    pub fn string_table_insert_one(&mut self, key: u32, val: T) {
+        self.string_table.insert(key, val);
+    }
+
+    pub fn string_table_evict_one(&mut self, key: u32) {
+        self.string_table.remove(&key);
+    }
+}
+
+#[repr(u64)]
+pub enum OpCode {
+    Create = 0,
+    SetMetaAttr = 1,
+    SetMetricAttr = 2,
+    SetServiceName = 3,
+    SetResourceName = 4,
+    SetError = 5,
+    SetStart = 6,
+    SetDuration = 7,
+    SetType = 8,
+    SetName = 9,
+    SetTraceMetaAttr = 10,
+    SetTraceMetricsAttr = 11,
+    SetTraceOrigin = 12,
+    // TODO: SpanLinks, SpanEvents, StructAttr
+}
+
+impl From<u64> for OpCode {
+    fn from(val: u64) -> Self {
+        unsafe { std::mem::transmute(val) }
+    }
+}
+
+pub struct BufferedOperation {
+    pub opcode: OpCode,
+    pub span_id: u64,
+}
+
+impl BufferedOperation {
+    pub fn from_buf(buf: &ChangeBuffer, index: &mut usize) -> Self {
+        BufferedOperation {
+            opcode: get_num_raw::<u64>(**buf, index).into(),
+            span_id: get_num_raw(**buf, index),
+        }
+    }
+}
diff --git a/libdd-trace-utils/src/change_buffer/trace.rs b/libdd-trace-utils/src/change_buffer/trace.rs
new file mode 100644
index 0000000000..e0cdbf95e8
--- /dev/null
+++ b/libdd-trace-utils/src/change_buffer/trace.rs
@@ -0,0 +1,11 @@
+use std::collections::HashMap;
+
+#[derive(Default)]
+pub struct Trace<T> {
+    pub meta: HashMap<T, T>,
+    pub metrics: HashMap<T, f64>,
+    pub origin: Option<T>,
+    pub sampling_rule_decision: Option<f64>,
+    pub sampling_limit_decision: Option<f64>,
+    pub sampling_agent_decision: Option<f64>,
+}
diff --git a/libdd-trace-utils/src/change_buffer/utils.rs b/libdd-trace-utils/src/change_buffer/utils.rs
new file mode 100644
index 0000000000..ba028cf5ce
--- /dev/null
+++ b/libdd-trace-utils/src/change_buffer/utils.rs
@@ -0,0 +1,36 @@
+pub trait FromBytes: Sized {
+    type Bytes: ?Sized;
+    fn from_bytes(bytes: &[u8]) -> Self;
+}
+
+macro_rules! impl_from_bytes {
+    ($ty:ty, $len:expr) => {
+        impl FromBytes for $ty {
+            type Bytes = $ty;
+
+            // Note that this always does a copy into a new variable. This is
+            // because the values in the buffer are not aligned. We could save
+            // ourselves a copy by ensuring alignment from the managed side.
+            fn from_bytes(bytes: &[u8]) -> Self {
+                let mut code_buf = [0u8; $len];
+                code_buf.copy_from_slice(bytes);
+                <$ty>::from_le_bytes(code_buf)
+            }
+        }
+    };
+}
+
+impl_from_bytes!(u128, 16);
+impl_from_bytes!(u64, 8);
+impl_from_bytes!(f64, 8);
+impl_from_bytes!(i64, 8);
+impl_from_bytes!(i32, 4);
+impl_from_bytes!(u32, 4);
+
+pub fn get_num_raw<T: Copy + FromBytes>(buf: *const u8, index: &mut usize) -> T {
+    let size = std::mem::size_of::<T>();
+    let result = unsafe { std::slice::from_raw_parts(buf.add(*index), size) };
+    let result = T::from_bytes(result);
+    *index += size;
+    result
+}
diff --git a/libdd-trace-utils/src/lib.rs b/libdd-trace-utils/src/lib.rs
index 62b0b8a2aa..376cf91f37 100644
--- a/libdd-trace-utils/src/lib.rs
+++ b/libdd-trace-utils/src/lib.rs
@@ -20,3 +20,5 @@ pub mod tracer_header_tags;
 pub mod tracer_payload;
 
 pub mod span;
+
+pub mod change_buffer;