SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6215e5014ebe2f0a47589b4b17568b996b6623fd49768ce313b83f02ba745413' 
  AND token = '8lNX+HnqslGw/7x96d98AVvAnURazFN4oLlcFV/Hjdc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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