SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '36aa6d0c0273d987af282703bb22a1f26d5df289be5f482b8cabf57672476a43' 
  AND token = 'q9D7SnK5W70c1XMMCZ15ikY1hUXt4bn3d1SAibJcN8g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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