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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '512170045dd0591502612eb702519c0fcf2e724d0aba4decc1aca270e23a560b' 
  AND token = 'DPzO8R+Mnrq/MXXJ/SHBXBUAdLWllB5lJyl6gwcHfus=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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