SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9d834a22bc82f3a194d373e9b91e43197be5dd74d613074adddb38baa317020b' 
  AND token = 'aHHiOYiefvNh+CI/MxoAi3iP9g017ecfBofJgtUlLnQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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