SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '83d2c18e253640d46cba37adfbe2cf4eb6d4215cac1e97462e71f546986d53af' 
  AND token = 'DimhgwLR6SiYxr46bji6DTPyOBB6mLMrH579LocBD1E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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