SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '36f7d9bba620ca376c2b7e2f6883e8c768310c6a3a36385635eded9d38623679' 
  AND token = '6wz1vrrAPy6JdrlUjMXYMfOlPibkpgxUwGU213k2hGY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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