SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'cb8f86e671c816155f646575988c285db293d69560fca1e849bbbf6497e57e42' 
  AND token = 'LJScuCCwpQNlHbEr2CLDwMaYMK4e6aOjy1G+N7QX1AU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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