SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c6df680b5c4cd2e2a8affe81a2a7f2333511e214d0492f057b4e5b3133bf5845' 
  AND token = '6F9VFiqYUMcRO2cMiS7YgpF7pJVeQBwn/lKnw/9Rla4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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