SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c37c68406daf8b01228302d6d39a069df8f2d0b38524a1815e491fa9f93eb5cc' 
  AND token = 'nAekMSErPxk1hKRrIFhcTjOPk+A11TyDuTYlzDtlPHU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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