SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '42d7c74ba59362ddf431f216a8eedcc43f3de64fb88db0a2cf936450aac04296' 
  AND token = 'mMT8SrGvfqsgXswQiUVZ346yjhgwf2WfJVxoU+H8vKg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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