SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a350d29d5268befc1b4f6e68eeff02078ab8d21f4eea4628406652111cad74d8' 
  AND token = 'f/2igdFSJfnv3EPJqJ4j1hUBJprCd+XrIBPlhMvshso=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00038

JSON explain

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