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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '946d2345a3a8be3e682003d4c54d8437db36c4b5fbe2aabbfddc59f631ce48f4' 
  AND token = '7YtZrkiFkx2qsZtAHUqNIB8tUt8ORJ9Bjaoh4pqrogI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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