SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5f008540677540feba5516239d818462550a1f670e511c7973a62a5800ac79df' 
  AND token = 'g4ZQ4yhnseGZ5PpY11IrFbg7Ha88Ee4JWbQy8EGjZMY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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