SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '339c386d86cd05aaacbe07771fc50b1193e06dc0bef25d35403aea975c573a02' 
  AND token = '3yEbjYvOM7yui8tXLV5Qz9HCdmyApNkIuvSj7tcFkjY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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