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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '8854c81e6ce0e0153ff0dfae3073cb0f48f98a4a7424cfaf88e0edd5056d4206' 
  AND token = 'oQNE5+YjV4tmX7IUENVmPHtSqgMTBCdaMYRaBCSMwaU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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