SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '79f394294232274269d7f94534bf04942655505effc1fb97096e494b44582e37' 
  AND token = '900pYoUGFWor5ZITdf00tbQRcR/nD6I05rGHd5F57fw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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