SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '76a21b5f58c1f670c4adda044e4a0ff895b7fa7a1c415aaaada844e8c847b593' 
  AND token = '/yLb6qCRmayKiiyXFEiaRWGPIjWC4j6BP4PsH2XKfdI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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