SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'da7e934f09824b6c3517e2ee8854a540d65f1622c8bcb06e14a40dd8f323b240' 
  AND token = '6A/xRssRMFrQncHIyeCsjVZ0SpCVkz2T+JVTr0bHrgI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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