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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'c826ca798119a0fbf32c724a03cf0231e9c8f8e141ad9de8c903c2cbea50bbb4' 
  AND token = 'sarF6P3/dToBzMBzjvwQ8fOkrQTChMceVZzpDDCRWjI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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