SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b2464485f02250dd4dc816e5e2ab43f68dcac728db073c815f28121d4feca9a3' 
  AND token = '8bUHW74osSb1+vuyJ5GCBZZ6hR9GNJJynH/RNVFzhko=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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