Aggregated size of all range keys has exceeded the size limit of 1024 bytes

TL;DR — DynamoDB limits a sort (range) key to 1024 bytes and a partition (hash) key to 2048 bytes (UTF-8 encoded, plus the attribute-name length). Your sort-key value crossed 1024 bytes — usually an over-stuffed composite key. Shorten it, hash the long part, or move the bulk into a non-key attribute.

What it means

ValidationException: Aggregated size of all range keys has exceeded
the size limit of 1024 bytes

This is a hard key-size limit, separate from the 400 KB item limit. The sort key's value (measured as UTF-8 bytes, including the attribute name) can be at most 1024 bytes; the partition key at most 2048. Cross it and the write is rejected with an HTTP 400 ValidationException — client-side, not retryable until the key is smaller.

Why it happens

• Over-long composite sort keys — concatenating many segments (ORG#…#PROJECT#…#DOC#…#veryLongTitle…) until the value exceeds 1024 bytes.
• Encoding a large value into the key — putting a full URL, path, description, or serialized blob into the sort key.
• Multibyte characters — non-ASCII text costs 2–4 bytes each in UTF-8, so a "short-looking" string can be over the byte limit.
• A long attribute name on the key — the name counts toward the byte budget too.
• Partition key too big — the same class of error against the 2048-byte hash-key limit.

How to fix it

1. Trim the composite key to just the segments you actually query on; drop human-readable filler.
2. Hash the long portion — store a short deterministic digest (e.g. a truncated SHA-256) in the key and keep the full value as a normal attribute.
3. Move bulk out of the key — the sort key should identify/order the item, not carry its payload; put long text in a non-key attribute (which enjoys the 400 KB item budget).
4. Shorten the attribute name if it's verbose — it's part of the key's byte count.
5. Measure in bytes, not characters — UTF-8 encode and count, especially for non-ASCII data.

Related errors

• Item size has exceeded the maximum allowed size (400 KB) — the whole item, not just the key, is too big.
• The provided key element does not match the schema — a key type/shape mismatch.
• Learn: DynamoDB item size limit