SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c63e99f9301337cdacccc3a09d405ddf52dbbe7045be66c29124580339ebc5d8' 
  AND token = '+OSAaoOiItvxFSdcrvuzC+l7iqSWwHhwIzVqQfLNFps=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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