SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '517051d7f3101594aea6ee7456182b66cc73d2cd327da8789ec1632720bfa1c1' 
  AND token = 'Ifo+85QMD2AwWoAZT535yQFNYNSOl3usXHZrdci854E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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