SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'a27be29cc6e2fe69b20f3abf76533ad26f04d7cbba6d7baef3cb02278bd4629e' 
  AND token = 'zhdUe4NvCm+NQkuHMYpSUzwlWDUjx+vzRCb7KyWaqjg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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