SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c3fc0c1d9bc2efdc6290895cddc58e694f52266e6b9b14b6afeddd7593eca2c4' 
  AND token = 'J7zHzp/jy+abtg4GuY8Kge1H98vj5Y2bZ7lDt0vhiWQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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