SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a78ea923c3802447863426f5f276e7f3c312cf6f55000b1458fd71b74125e184' 
  AND token = 'SCQcxw48jRlGpxHNxO/NXH+g5BSmb22wzvWjjmfvU3c=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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