SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b3b8536ce03ab7c49769902fc941c9c338b72b7fa8ce14c3c0d986819cb4ae17' 
  AND token = 'eqjrLe5LGHSO7i2Yu7qBwo2Ike6vgwQjKLVrIouE8zM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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