SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4d15b0331ed23af941af6426512f3ae58ee2feedc666a3c948d515434d81a3ca' 
  AND token = 'cYSWR9P6XZp3o3ac+3FnN8Jw36w8coDCH58JWYXqKsg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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