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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8c63d6ed2d23301e5c69e4dc69eed19f1dfe9130283194abb377e5a2da6f4826' 
  AND token = '5zVD85Guf6Pqj1v0MZv0kkL+8vSCYcnWn2o7iGb2gD8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}