SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '75951d892c5e53515fa710913c0c65aaec57b9957b4e85813985c4abdf93deef' 
  AND token = 'TzTe9jECmgXeJBM5OvMg4plGBVC+iDg2Ok1/Tlh+trY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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