SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7874bb5edd3e24a7993e467ba8a49844bd1b5b39a72d1c9cc8775185c5add911' 
  AND token = 'cQ5WvJKuNVhAtIIoTP/BD10y8fci0c5fmv7i3J4aF1k=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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