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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '5e4d6a92b976b7e23f0dfcb62b59206a751db8ee75ef7469e99e44437a5a4232' 
  AND token = 'QhIjhhaaan5vvunpkz+HWQu9ACEeDHV1rCnvY/nUfg0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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