SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3513238787d698057c2d8b10e7bed92fb06c583b7839e885427c64242797fea8' 
  AND token = 'MGzvouipakJvNSp6nIzCY/wMS/29veCWtd9uXMPjhOY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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