SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c353de28e073e32f68dc61d1dde192149815508e3d564fc2f6eff786aec01f0d' 
  AND token = 'Z2Eom1Ixj6JJAd9h6hKHiCjuhMDG7nVZj6Bw6I19EOk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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