SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '56a15710feaeb1a8301a9b66127ef473b6910648b79d1ebc4340bb06e04be400' 
  AND token = '6KCqZMtKgzg/VR2+du5RD1ce1Vqlpc8dyG3uLTPtsYM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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