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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'c1b9844620f418295cbca083328a9b367db5be0e944e0dfeb5cc38e4c42c1f97' 
  AND token = 'rF9BHRXXymErBoRyJKvNaf45ioHxpqpCekmGiSm1FiQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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