SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a38fcb8680d8023adda14482c76c776542910d147a53b1183e0dd5a42856253f' 
  AND token = 'Rq1dJlG1jrLvLlHn7YHMABAie49ea0zWgoEFcLBmCKY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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