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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '847de76f8ec88ebbf6eb199c018c9eea5edecf12d028f9be969ae0bdc539ece4' 
  AND token = 'iwzjiUqPFh1ud9uDpcJtcoyK6WDs5O2e37D8W7ZAFzQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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