SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8d35c58642ca028d5e1ade24385dad6ba9937d1a9d218bc569b01b09c89208b5' 
  AND token = 'vHrYgrYolOKCBBs9BQz5sb7mG/bC2ivvvjB7jYrKPR4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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