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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '15d031d19d2db7d2eaf362d6418d8d1dd353a439b0346a0cb4e699861e94ce88' 
  AND token = 'MU2aMP4KmXhCOGSfw6CTC2rsAsLd5kAnWU6Rjuka9sI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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