SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a28507b5951b66633ff9950edf52bd8637797df1f5099a2759acce8db75985db' 
  AND token = 'PCmjFuOLxnzZrUyOzxAEVfiTOsYsg2xrFeLvYpliUmE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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