SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '15c46ec490f42e930292accf739a610e437f994a4c2016052dc28da7525f0b9a' 
  AND token = 'mHSE+RwQgfO/BsqtkZLPirORSyAXlVoU0c6qTum/hrk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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