SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '90a851c77983b6d487d1cfb6f5e4fc6651cb1a3950baab4d570998fec6b95868' 
  AND token = 'kCwEXSZj3ukyV/GLdoiwIT/necOnAd+IEWlzePs5oBs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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