SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '709540d8dac48d761048a212351f4d305b1d43497c7b1e5f0f601135624ace96' 
  AND token = 'YJ6v4dZNnzExXTqhPHcBHT8SNgBsRww04jYEc2EuXLo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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