SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'eae31bf7fdd127acb4c46c1d4e7ca8961b121ac9a7649f182e29642852902840' 
  AND token = '+6IIu1brmCyTpAJuMxmncqVCMq4mHksSMkViGXIONlA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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