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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '43330ef7142107c134139d3153cb487bb3e101da8a3abdf45123a735464bffe2' 
  AND token = '2fIy2a1J/mWKBse1clabUvWm/R+RtGYbny1xRlOms7A=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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