SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b30fdd324fb79fd965979340c291051bb4beadc61aca677f815b401668a123f9' 
  AND token = '4abue8zyoWXMYpTEAIEAd5kefKqQV7UTQQntCh2hqxU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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