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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c3ebffd5f0acd0550d5d018103d0a6846b5d0ee34ca0c2e550dee40cd8eb1d61' 
  AND token = 'OMkuxUyj7kpP30SGa+WIL6Hnmxs9fOCcATdsV3++QMo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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