SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b3b7663fb653119714a9b1b4bfcdc0901f4c60685d04bee819fd0d83e9be5745' 
  AND token = 'CUQK2B/L1VGgaXyd8HnRjEFxXlq9NngkwO8oJGCn6GI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00038

JSON explain

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