SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fdf55bc10ea98250603afc59cf6637e264030b2c3f34177a62228f1373e3fea1' 
  AND token = 'V5xGCsLcbbCOgWRZTZYrDc7lp/IoVnU278b1VgOk8J8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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