SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e596f6d30a4db607299729465388655bfcb00741f635838c6553138b501379f4' 
  AND token = 'jvrGv1plGd/NipagIJduWMvHAPLcgrhCOVDdM44WeVU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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