SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b971096fcaa5db4fefad237182b96f0a2f6598ad373880446699ca228be3a2c8' 
  AND token = 'OiPDhXF35mtIzjmT+/Sly7JGGIVtAbhbps3Nsvckt+Q=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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