SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b28046322e236e715aee187730b51f2e3c2277327b20726470f727bf9a4b440d' 
  AND token = 'p5f+FAmdYFMRwNvbAF6AIqnK70xMEAUi4oRtqXlMPYU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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