diff --git a/sqlx-cli/src/prepare.rs b/sqlx-cli/src/prepare.rs
index 95df2c54..fa166f68 100644
--- a/sqlx-cli/src/prepare.rs
+++ b/sqlx-cli/src/prepare.rs
@@ -5,6 +5,7 @@ use remove_dir_all::remove_dir_all;
 use sqlx::any::{AnyConnectOptions, AnyKind};
 use std::collections::BTreeMap;
 use std::fs::File;
+use std::io::BufWriter;
 use std::process::Command;
 use std::str::FromStr;
 use std::time::SystemTime;
@@ -32,7 +33,9 @@ pub fn run(url: &str, merge: bool, cargo_args: Vec<String>) -> anyhow::Result<()
     }
 
     serde_json::to_writer_pretty(
-        File::create("sqlx-data.json").context("failed to create/open `sqlx-data.json`")?,
+        BufWriter::new(
+            File::create("sqlx-data.json").context("failed to create/open `sqlx-data.json`")?,
+        ),
         &DataFile { db: db_kind, data },
     )
     .context("failed to write to `sqlx-data.json`")?;
diff --git a/sqlx-macros/src/query/data.rs b/sqlx-macros/src/query/data.rs
index 33055816..ee123b50 100644
--- a/sqlx-macros/src/query/data.rs
+++ b/sqlx-macros/src/query/data.rs
@@ -40,6 +40,7 @@ pub mod offline {
 
     use std::fmt::{self, Formatter};
     use std::fs::File;
+    use std::io::{BufReader, BufWriter};
     use std::path::Path;
 
     use proc_macro2::Span;
@@ -60,11 +61,11 @@ pub mod offline {
         /// Find and deserialize the data table for this query from a shared `sqlx-data.json`
         /// file. The expected structure is a JSON map keyed by the SHA-256 hash of queries in hex.
         pub fn from_data_file(path: impl AsRef<Path>, query: &str) -> crate::Result<Self> {
-            serde_json::Deserializer::from_reader(
+            serde_json::Deserializer::from_reader(BufReader::new(
                 File::open(path.as_ref()).map_err(|e| {
                     format!("failed to open path {}: {}", path.as_ref().display(), e)
                 })?,
-            )
+            ))
             .deserialize_map(DataFileVisitor {
                 query,
                 hash: hash_string(query),
@@ -107,8 +108,10 @@ pub mod offline {
             ));
 
             serde_json::to_writer_pretty(
-                File::create(&path)
-                    .map_err(|e| format!("failed to open path {}: {}", path.display(), e))?,
+                BufWriter::new(
+                    File::create(&path)
+                        .map_err(|e| format!("failed to open path {}: {}", path.display(), e))?,
+                ),
                 self,
             )
             .map_err(Into::into)