SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '78f98a9c7b8d376e216664cc6d205cf4312c21e85a34ca22c9b5a494e800a1c6' 
  AND token = 'BQU/EzwjIT6TxAg+PZq8eFaM4Cu+9noHXl3JRbUZgtk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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