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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '53685e274d7fd12533bbf00b002c4a1b5c42646a2a29576fb0014d351e4a58d5' 
  AND token = '5KLlGlK5DDQ6sZ0tiIPp8BTE+onu+Ak+vWHGQY9T5K4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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