SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '835244e1d9d1de96d39702b276ea3bb6dee0a4234e759dadec343c41a3e83bff' 
  AND token = 'JQYYIeiBHiNUly3dnlkZ2X4bEabgsGRSI889el/ZPqg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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