SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5b090e3dc5a8e568c49d1e6b3c666ffd25bd1ead90fdc638ce1849f7044f6882' 
  AND token = 'tUDTyFX1FiiNUNelQP8brDrT+ARS3q//OLAYhmMkhwo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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