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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'ad2723e1acdd0d9b3b0a403b51ceb1258b73e812ae3c65ff55bd10ae7e47303b' 
  AND token = 'DQHLXkPG7+rs+LXg5uOAlkknmZ35U2HdwWUrMaMLJ+I=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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