SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '17d8af8eac341675472cd6cfae70441997867bfc92f9471272cbf16bde48b365' 
  AND token = 'sNr/7XEgh6nm4kBF8Cf4wmot0OXOWMDgFnchCBk0irY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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