SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f15399df6a395172140b46f1042245e81207976e874e93e307c09835b0da2534' 
  AND token = 'SfZLHeDysxC0nPEz0XlLPGu2ir6NpKFlMyEI9v/zb1k=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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