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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c55c88ae76d6546392847b934266efb580ec54a60486767867a8bf442a4fa709' 
  AND token = 'rK2clz7xUIYyZKCKT3/GMSzewS5id3WlEy6gM3t3PiQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}