SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '811fd5e9e70781e28d1970eccf0c91903b7f9c299f9f2a15012c2141841d03c3' 
  AND token = 'T2BBUb3TFW1ZNnQNGCK1/CymxaaWzfWV7upJ1P/Z4WI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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