SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '55951bfb7875c8e5b95292507c50fcb3babe2dd3b353d85ce8d0fe289035c7d3' 
  AND token = 'OYpskMlPGj8xQ9T3wBRVmPFEdHqMRuypc4dHwhaxMK4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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