SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fc3591ceb362c1751f82e9a88772952d0276f64d99197f85ad6d339a399867ac' 
  AND token = 'xz+Get4FDpHPvxLxTiGGEzluumo7XdDD1ut4sd4dVvg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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