SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21f2073a27e65fed61424335c717eedac028eed7ff8c7a4ae4e855a23458cf3c' 
  AND token = 'FEoUIGvLB3evy4bdqibYJWOX/SavFTFE4NcizyHSG40=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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