SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '2aff48657ad4fbf3ea2d19a971863ea80e9b5c403a816817b4543ac85572af97' 
  AND token = 'KbJAVVCLL6+vakj8RNRbx1pvblzEg6vBMiHtSYVQf6Y=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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