SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '56fa46bfacb7b27231f7819ade07e796600c38391c2ddb61b48e7b4d504f8f5a' 
  AND token = '0OXZy2rppvMwUy3lBsBjBqUJdp8ozbAr7nLE0gVRrvM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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