SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3fa537d8166ed5147571922e994134b770f45caeff2813e0beda0f8997579b91' 
  AND token = 'Ns9Pf+uiERFLEBRj70Mba5Aazzode5CSw/DGmz9nCjE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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