SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'db6dad94539070cef4f50fbc2c711aac44bb5a79064db18b1d43eaed81381522' 
  AND token = 'hVLPOJn30khp4pSUju5xSPDwZtiELEpXLvaD87zVPqk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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