SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '868f27ceca8efdb1bc2f117faadaf683573acd3e06d747e6f363c739d42df4d2' 
  AND token = 'NcSHO+SV6xGa36nNUPYFBD/Ic2dNOMfZKxGkU+JBxFo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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