SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '54b0e040e3c1869c494788f2060d698be669e4a0a3b73c7b8657d8a5f093c62d' 
  AND token = 'YOArLb57jKlTjPLGKEPkvrBTv1zEiggZoiz1VeHVfgM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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