SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '976cf35fa5a0a0c0b6279b961e81db323f960aec11aa042506538a3821c1ac10' 
  AND token = '3CXBBeIcwQqPquWruuuCF1YRpyFbY25Isfiu4SxikkA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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