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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5c6437bd3010c92330fb333a0ddd0e45cbc00b11e26e8c12920794ba677a8a53' 
  AND token = '5fJ3nuxgnBYW2gzXgZqIoeFOu+mRpCKMQ2Z0+F9OIa8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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