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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'aebd183f1b0a31a4fba42de970a81e07ca29024ab20b19a0d6f6eed9a8608e79' 
  AND token = 'Sr5e3pHp1QpSAZmyB8pHEfDx3NOdxuYXzRgu2+zMOmA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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