SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f7b38f991b0d3e4ee6e527f9447d6f01e8541abe69d6711eaa7dfa7a312641da' 
  AND token = 'LfZ8CfT2GXWObnWWacetnVluDm7Iw7RxbngUclT2Pso=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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