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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'a09d02ef20a928b319142c34950a9b0d52eb30c111985a242af310c12a36a018' 
  AND token = 'ATKmN3V8Fvew3fThYo4ItcQ3+YCYzCpDGgVbxrUJNCU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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