SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4b66939292aa70732b28075b41efc4a988a814c7ffdb089ea0bb8a81a5991dc9' 
  AND token = 'JK/XlzANqSzC7Dep7nVSj75n3XLEYqZPvAA6HeuUzjk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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