SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5fccc48bacb901e81c220039480447b2d621f507ca6947923ad75586409112f3' 
  AND token = '9krazkRUDL5nTbdu+ubZ2u8Rk7WOGExyvGvSM42d6kU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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