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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '509369acaf23d811fb7d7bf96064bd9c089381a03d8fc4cdbfd9f71a9d6d8a78' 
  AND token = '1ZuRJsOZagafVk9TB5bdbnR76soxcDvCleCF1RnumGI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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