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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3a577e6992870ff417bb31614f691a57e7d63df4f5b9c6bc278bb9652e06ad51' 
  AND token = '1aTWRTMWITF8/UxcgLyKaRULbyXHL//YJKAp1MlWqSM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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