SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a819234496f7bb4ff14c40f835d0ae1ac875be1a52dc75ee282f198336375606' 
  AND token = 't5agL6k5w0iWw/IytiTN9CJr2BXeeLBqQXPT1nIjccI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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