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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '50e5816392180710f3019675fc5b3db30459703b3bb985a3a40920816adac463' 
  AND token = 'UJLI4DURl3bo0pctiYfon9pUeyZOTJ8M5SQO2Bf1/v8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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