SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '303648e591b3d04eff440c70854168fd58b9e607e1f7c6a896f319be8ca59363' 
  AND token = '+AsPJ9FGs607xuXL3mwSi3FBjgdzdJYUr5bvRXKGwWY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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