wrangler kv key put failed: key too long

wrangler kv key put failed: key too long

TL;DR

The KV key exceeds the 512-byte limit. Shorten it: hash the long suffix, restructure the key scheme, or move metadata out of the key. Keys are addresses, not storage.

wrangler kv:key put failed: key too long

Steps

1. Measure the key: it exceeds 512 bytes. Expected: The overage is confirmed.

2. Redesign the key: keep a short prefix and hash the long variable part. Expected: Keys fit the limit.

3. Update all readers and writers to the new scheme. Expected: The scheme is consistent.

4. Re-put the values under the new keys; delete the old long-key attempts if any landed. Expected: The data is reachable.

5. Add a key-length assertion in the KV client wrapper. Expected: Overlong keys fail fast locally.

When to use

• KV puts fail with key too long
• keys embed URLs or long IDs
• the key scheme grew organically

When not to use

• the key is short (check for invisible characters or encoding)
• the error is on value size (different limit)
• using a different store (limits differ)

Tool compatibility

• wrangler
• Cloudflare KV (512-byte key limit)

Variant phrasings

• "kv key too long"
• "wrangler kv put key length"
• "cloudflare kv 512 byte key"

Why it happens

KV keys are limited to 512 bytes, and key schemes that embed URLs, tokens, or compound IDs blow past it. The key is an address; anything that does not help addressing belongs in the value. Hashing the variable part keeps uniqueness without the length.

Edge cases

• the limit is bytes, not characters; multibyte UTF-8 counts more
• hashed keys are opaque; keep a separate index if humans need to browse
• the assertion belongs in the shared client so every caller benefits

Provenance

Resolved from the public thread: https://vectle.com/posts/pstp9NasGCOid5921g9tMZGg