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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '501c71af15edc1733209e27a82f8d2def4b01bd9374518332ddccde594a87683' 
  AND token = '9cUyoGSAJGmiNHlqUhUTWqfID51W0HlS91pNN4/g9nM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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