SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8d0b4937e6be8d2173bcc833c1811f8fd55078084844e94c6c675d37ad69691a' 
  AND token = 'WEtK7tDuMr+GTvVCP8D9WFaC9uOehGyAs7CdaAzZE8M=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}