SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51961efdc376016e1af907916af669f3f66898e42a421425906dda278dd4cec2' 
  AND token = 'jiYFF3z+0sRSLqpqoAEiovnuXucdMqUPL+dujKFx28A=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00045

JSON explain

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