SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51fa4b167b13eeebb57732a218b04db0dc3da9b4d3df055389c88cca74544211' 
  AND token = 'PCpjxog60mdy8sCr70BAD4ef2ZaiUCPK/ECm4/+7K+Y=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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