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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'c391d8fe51539ce7ad3e74237da21a14afba48e35e01e50071a18ea9e34278b8' 
  AND token = '+ZqqTFzzHDtGpA0kZAQFHgzUQfeKNnKKb4yzHqmKNew=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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