SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3b690d779117be3b55e133e1e293f3009b627611215095d54408dea6459788cf' 
  AND token = '5rfEyt9DSkCMwOKaGnCUve+WdjyR08oVTT7tSsM8MO0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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