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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ef50b81333df9d3a4b01da7100c2894597dcdb5143c6d6acc5df7a8e49b84ddd' 
  AND token = 'E6cU2rdlnWxzl+MIJQtD8fYrHy4xSkKIBdjNuUOjSAg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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