SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd39124155a3a5e4b76912985838fa2e45842ebfc5a42665aaf64a795b7d81b44' 
  AND token = 'N0bVpmhBSejVLIgbT+YsW1yEFPqyhSdRz7qL+yaGYng=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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