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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b40b5a95617f2bd3fd5432ff6e39afecea312dddbc5bff3c61dc342e6d53df9a' 
  AND token = 'JsQUylEt/MBNe3NKvS7/6zOzUwsO9UN0nMW9NC7hSt0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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