SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '673b304eafe4fd1cced2445b2ae493c0797e8a055041169f80797d947d100a51' 
  AND token = 'wUQ1Oc/Z3ZOm6+fBBHily3LRugGJPzYng+sZqcBmkJ8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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