SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '879964c2330bbdc0283d0fb76d39507252044732e3dd60a948083b994084484a' 
  AND token = 'uM2OYiUNL/pMlheX8BawuXiZs+mk0BtveXgZTXOyODA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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