SELECT 
  1 
FROM 
  cscart_june_setuplock_keys 
WHERE 
  key_id = 'a71ce51a979bb3ae3bd20ebd3539f9bd38cc3054bbe7f174c022ebaa78da41c4' 
  AND token = 'CyQRqa/ZsJx46c92QuGDK+S6mP+mq+dzZPxR7RKiNKI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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