SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b16b5d01a70be24ba262a081f2c6731a597668d5d02fa98d7806c2e9779a9155' 
  AND token = '0zxBLhf39mLPjTP4w9py6vSQ9K5BLpBsJ+qzEnpSGLA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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