SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c5e039f52ebfb8bad591e6ff43b49abd0c90574a0f3201104ca065ec21557402' 
  AND token = 'stNlxMQqvByODK0WRdJuFgDUB0WOL2/AFekugUTElAk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00064

JSON explain

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