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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'df7f480690ba401f8e2e7ecf8e915cb4425efc6f4d00f8f837585a449ae9f744' 
  AND token = 'pMGO6NkxcyHF6Tr+tAG+a3Mq5tPZmLehIqHN0+H8rwM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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