SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd88d64a2eaafa233f367c5f5eacf795c2b4c18ba56d80f8e19dd09d8a989f168' 
  AND token = 'IuxSitFWaRifB2NM1h21nkHUxnaT+isML7PCbSf/nFI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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