SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '87973e4ea86f84904c65fb6cc97afe407570a68e381745904f0bce6b7fb85873' 
  AND token = 'SKKLh8ayzdazqM4T6XGzjxqExjcM3zKwvd5jCcgPeI4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}