SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9998ef1424d3e4efc4cbbe0c5d5da50360a38481aa11b31137873d5427c296b3' 
  AND token = 'hft/lwNOFXOtVoiLu7AUz5CS4TZ+N8sBl/97jlzS6Gk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00053

JSON explain

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