SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '87de860f4c03a8290713a703d161795848e94d6eba11256559395a8181fac357' 
  AND token = '4kcC1LA1FLWWDJ2/u8q4i5Ru8k1xidFKxlM2MrgIWP8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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