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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '950227fdf2df37bcdb32c4399243af38b621443503403e15ba6f399c50c509a9' 
  AND token = 'U/QtnkTs1nHO9PEfx0/VhmUE3O5+bvWXnMEu0fkGWgI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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