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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'eef04ff20ffdac4a1c94447e430428dd80d4676eb847e77fa79f53aa71939107' 
  AND token = '+PKG6liAycux0BUNlJ3/+OK5yYcmf78wTbc2uOPxPIY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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