SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '991e50b5bc184486ffa2c92506bf61d7805f8cb0b28ee764468f59c63506d92e' 
  AND token = '63hW6mfqhQDOL5GYaw3u+VEouccBrA4ck3EDUc9bU7s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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