SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd3d5c9415b5004d1c7926870264a0404159c870c8f499797ee2def049919cfc6' 
  AND token = 'uCYDsGSVyg235Bvfr8wkpNJgTRaVoAyUscjaoKjvSEY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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