SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ff3323ddcebe9b5b2924a966d053910f7bfcc67f65b91fca40515eddf6a076fb' 
  AND token = 'xiYwVTgQ8azDjVpddhiE+kMMRLpyuKBJmmwMN9Q0YUs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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