SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'dc5d540817e1f54bf176c122637c7f6c4e6f36c9eda5977b7c54d44898b94be0' 
  AND token = 'p7PETrZVOAVIYehK68lPTNzBlIGreAy8YHSsfAxggsI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00056

JSON explain

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