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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '2471b298689d64df977276ab01892ce312af0899985c3b4cf2cf7f7141b596f4' 
  AND token = 'xhY4g0mlb2aq+PW5G505Ninw/Tha5DT9UPg8HbHm4Ec=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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