SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6ce543a1cbd34037bfe1c97ce54a22701e2d20a6972cde4ce629584d2d969937' 
  AND token = '57+qA8I+eNulkTr5xisXjCJGh6PAOy9ncHyy6TCammE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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