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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '78cef1a8c0ac686f35492e68510fe8785d316dda3c23656bb1b49e5a9aa21bc0' 
  AND token = 'ehNvg2qIJcXvMYpB0bvSCpYrZGPsTNNykB8g68AjvGs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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