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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8790c6631d42317cde0a741457b3c24b3c7b75e2d16dcd499df7f08cdba89bf6' 
  AND token = '9wRPvQXFojP2Z2tMu9TFk9NQ1jcYmDUCYe3fZ6gJKWE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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