SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '758243423e91a1bed88ec0602fb2bb08799467a3e70024d029d4a88dde2112f8' 
  AND token = '0n8gZLfrMyJFD2m8Krdk2aze7xQs+qXDAFmSi0AU+bk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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