SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8fb82571fa1437c05d351a018bc3ef48278b3da61de4a6adde8e0f5438ab57be' 
  AND token = '3SdlYSEoWms+V8mrmIXPgbEbstNhHpygBT4sdQPLc4c=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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