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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b4ad688aa05ed15fccf6529e477f71d75ce48b3b9624aeb24eacc44073e3e423' 
  AND token = '0zrYnIUvjM/ZSAvbnRaUhY7klRvmnptoXVU9jGZ6Ns0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00016

JSON explain

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