SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd51337b0d0f3c52b8e6581dd9f92b182dcb63506101435440c30a251f223dc4a' 
  AND token = '6WHNlwaoSiARXzYdSsezeSw1HT5eYSw7cduPahk/I30=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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