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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '781909121419a30c188f8c7b7fbfd030200bf37a6e0ab952fcb16ae3c9381471' 
  AND token = '9PDvDDd6MK0tyimN+v1qnf6hgnEORj9e/APAG2mup80=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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