SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'af4998ab3c0536ecb5884d531435b8753090b312fbf3fea6a86911b305ad61db' 
  AND token = 'tcCOpCBJ6LS1KStVhg78gTF4SPOdVr/UCPxauuDokB8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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