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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '50678f1600f20a4bfbf79857ed175ade4ef63f09436a5e2f3c8beeed3ff2d44a' 
  AND token = 'oSe+LLbV6F4s+oX3IXxgTn3f3zfmWviX7JTsqnX+K4A=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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