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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a3dc4a28ec6806a2fea31f7fdcb311db6e81fd7bba96cdd50018fc671c46f561' 
  AND token = 'n1Rb5/vuzppQzFWUeBt7fQx+f03FT8wuxLmso+E2y1s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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