SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21308e561d44bb749578cac30a1d9afce2fe690bf5db1a586dfbabd4a34f93f8' 
  AND token = 'k0vr8ccTukij1hiUKx3lAk2lrrzNoYxgEBHSjceF2aA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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