SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6a0ef520004e4752f93fe60f1ced19253d2123b9ae749576573429cfebe1da08' 
  AND token = 'kxC4TArAbizvLuDo57tcuBs+zggKQM/leuc+npxFM7w=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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