SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6e341292c187c3ba64c21ee7a68ad9da35d68c5776b3bdaaaa000ee39566c75' 
  AND token = 'AS4wSNF/wtqBAEpEYZOJ9ocjo8iRcFEtihv6EOPSTkY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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