SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b56d473fdf3fe5507dd382ebaf8f025f6d8dba2199ada0d7b555912cada40d1c' 
  AND token = 'FQFCV6MKv5CndJOyzfieR95t/hsRL9803v7JTjicluo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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