SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b3cba221fc9b9ad977b813488f9a792b4c02014fb565fc93473597109eeac466' 
  AND token = 'n0Ygn5Xyvl5UReUOQv27Vxm4zTsh1b2YRLXmEVQpJHI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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