SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b52e7eb1bf1bb5b60e6a48cea70bda5037e2520532dd96d328f3fb0b341f58ca' 
  AND token = 'Qv/TOLifk1mdLwo8k9Rz/5ZCiOEbJ6k/qaDo99aLKZw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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