SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8db451ffde317158526e1f03e479596384cd64f4b24af53f01383afb294f95aa' 
  AND token = 'Ur46rQcEmU+M9UucxP6hirLZXVO2+rFb14fZfMzSXU4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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