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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4ff76e4bb700cb97dbd51c52cdc2d67ffe39f1767142556096a4f19d33b1eb21' 
  AND token = '5t68S9ST7For7uKDbR4HMbj1ai1IWThZ+H3K12YcMsM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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