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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6e19a0a270d8d9ff39d2be0380ad717c91a5bd98021dfc145c0cf8471ab3715' 
  AND token = '+1SGuhUaqOlIofjXs8axTSJAdfBO0BUFdTdgwPKhR20=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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