SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6a873f28e0bc776498b814c8f322eff3b3d8cf137a09e582e19032220f26831c' 
  AND token = 'NOO3YOzGuShQqt9kzRKuJS1V0ND4qr++wFYr/m8SgF8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00059

JSON explain

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