SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '563ad42a790e4553653164902a0260665bdcca6b69ffe62d258585d38a47a959' 
  AND token = 'h3yyJlErudC4ac2PWmZxlIaMuc9mMF+yBbWDhL5YIsY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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