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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51a74d023b7b6e9afa448b2d8b6b570c3ddffca3bc1d118a16a5d22fea11f3a7' 
  AND token = 'UoIkQPKOhXuTzXaPfXIcp8ozyihVxjmESMAyUOM3TAI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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