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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'cf38e9ffc982a1abbc2b1b18fe8990e7075b6113d63e4217ce339300097b5c58' 
  AND token = 'M9zAKGhTJYVZ43Y9uObLnI/I8Z4FI5p8wbfew7qdfbw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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