diff --git a/Cargo.lock b/Cargo.lock
index 6e49b88..034a25b 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -59,6 +59,15 @@ dependencies = [
  "tokio",
 ]
 
+[[package]]
+name = "atomic-polyfill"
+version = "1.0.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8cf2bce30dfe09ef0bfaef228b9d414faaf7e563035494d7fe092dba54b300f4"
+dependencies = [
+ "critical-section",
+]
+
 [[package]]
 name = "atomic-waker"
 version = "1.1.2"
@@ -196,6 +205,7 @@ dependencies = [
  "objc2",
  "objc2-foundation",
  "objc2-natural-language",
+ "postcard",
  "regex",
  "reqwest",
  "serde",
@@ -217,6 +227,15 @@ dependencies = [
  "tokenizers",
 ]
 
+[[package]]
+name = "cobs"
+version = "0.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0fa961b519f0b462e3a3b4a34b64d119eeaca1d59af726fe450bbba07a9fc0a1"
+dependencies = [
+ "thiserror 2.0.17",
+]
+
 [[package]]
 name = "colored"
 version = "2.2.0"
@@ -292,6 +311,12 @@ dependencies = [
  "cfg-if",
 ]
 
+[[package]]
+name = "critical-section"
+version = "1.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "790eea4361631c5e7d22598ecd5723ff611904e3344ce8720784c93e3d83d40b"
+
 [[package]]
 name = "crossbeam-deque"
 version = "0.8.6"
@@ -441,6 +466,18 @@ version = "1.15.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "48c757948c5ede0e46177b7add2e67155f70e33c07fea8284df6576da70b3719"
 
+[[package]]
+name = "embedded-io"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ef1a6892d9eef45c8fa6b9e0086428a2cca8491aca8f787c534a3d6d0bcb3ced"
+
+[[package]]
+name = "embedded-io"
+version = "0.6.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "edd0f118536f44f5ccd48bcb8b111bdc3de888b58c74639dfb034a357d0f206d"
+
 [[package]]
 name = "encode_unicode"
 version = "1.0.0"
@@ -693,12 +730,35 @@ dependencies = [
  "tracing",
 ]
 
+[[package]]
+name = "hash32"
+version = "0.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b0c35f58762feb77d74ebe43bdbc3210f09be9fe6742234d573bacc26ed92b67"
+dependencies = [
+ "byteorder",
+]
+
 [[package]]
 name = "hashbrown"
 version = "0.16.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "841d1cc9bed7f9236f321df977030373f4a4163ae1a7dbfe1a51a2c1a51d9100"
 
+[[package]]
+name = "heapless"
+version = "0.7.17"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cdc6457c0eb62c71aac4bc17216026d8410337c4126773b9c5daba343f17964f"
+dependencies = [
+ "atomic-polyfill",
+ "hash32",
+ "rustc_version",
+ "serde",
+ "spin",
+ "stable_deref_trait",
+]
+
 [[package]]
 name = "hex"
 version = "0.4.3"
@@ -1391,6 +1451,19 @@ version = "1.13.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f89776e4d69bb58bc6993e99ffa1d11f228b839984854c7daeb5d37f87cbe950"
 
+[[package]]
+name = "postcard"
+version = "1.1.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6764c3b5dd454e283a30e6dfe78e9b31096d9e32036b5d1eaac7a6119ccb9a24"
+dependencies = [
+ "cobs",
+ "embedded-io 0.4.0",
+ "embedded-io 0.6.1",
+ "heapless",
+ "serde",
+]
+
 [[package]]
 name = "potential_utf"
 version = "0.1.4"
@@ -1597,6 +1670,15 @@ dependencies = [
  "windows-sys 0.52.0",
 ]
 
+[[package]]
+name = "rustc_version"
+version = "0.4.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cfcb3a22ef46e85b45de6ee7e79d063319ebb6594faafcf1c225ea92ab6e9b92"
+dependencies = [
+ "semver",
+]
+
 [[package]]
 name = "rustix"
 version = "1.1.3"
@@ -1693,6 +1775,12 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "semver"
+version = "1.0.27"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d767eb0aabc880b29956c35734170f26ed551a859dbd361d140cdbeca61ab1e2"
+
 [[package]]
 name = "serde"
 version = "1.0.228"
@@ -1809,6 +1897,15 @@ dependencies = [
  "windows-sys 0.60.2",
 ]
 
+[[package]]
+name = "spin"
+version = "0.9.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6980e8d7511241f8acf4aebddbb1ff938df5eebe98691418c4468d0b72a96a67"
+dependencies = [
+ "lock_api",
+]
+
 [[package]]
 name = "spm_precompiled"
 version = "0.1.4"
diff --git a/Cargo.toml b/Cargo.toml
index ae9e283..4ee5a9f 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -20,8 +20,8 @@ path = "src/lib.rs"
 
 [features]
 default = ["cache", "tokenizer", "colored-output"]
-# Translation cache with sled DB
-cache = ["dep:sled", "dep:sha2", "dep:hex"]
+# Translation cache with sled DB + postcard binary serialization
+cache = ["dep:sled", "dep:sha2", "dep:hex", "dep:postcard"]
 # Claude tokenizer for precise token counting
 tokenizer = ["dep:claude-tokenizer"]
 # Colored terminal output
@@ -46,6 +46,7 @@ fastrand = "2"  # Lightweight RNG for retry jitter
 sled = { version = "0.34", optional = true }
 sha2 = { version = "0.10", optional = true }
 hex = { version = "0.4", optional = true }
+postcard = { version = "1", features = ["alloc"], optional = true }
 
 # Optional: Colored output
 colored = { version = "2", optional = true }
diff --git a/src/cache.rs b/src/cache.rs
index 4f56fa2..8825a28 100644
--- a/src/cache.rs
+++ b/src/cache.rs
@@ -176,7 +176,7 @@ mod cache_impl {
         /// Get cached translation if available and not expired
         pub fn get(&self, key: &str) -> Option<CacheEntry> {
             match self.db.get(key) {
-                Ok(Some(bytes)) => match serde_json::from_slice::<CacheEntry>(&bytes) {
+                Ok(Some(bytes)) => match postcard::from_bytes::<CacheEntry>(&bytes) {
                     Ok(entry) => {
                         let now = Utc::now().timestamp();
                         let ttl_secs = self.config.ttl_days as i64 * 24 * 60 * 60;
@@ -190,6 +190,7 @@ mod cache_impl {
                         }
                     }
                     Err(_) => {
+                        let _ = self.db.remove(key);
                         CACHE_MISSES.fetch_add(1, Ordering::Relaxed);
                         None
                     }
@@ -203,7 +204,7 @@ mod cache_impl {
 
         /// Store translation in cache
         pub fn put(&self, key: &str, entry: &CacheEntry) {
-            if let Ok(bytes) = serde_json::to_vec(entry) {
+            if let Ok(bytes) = postcard::to_allocvec(entry) {
                 let entry_size = bytes.len();
                 let _ = self.db.insert(key, bytes);