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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e29974b71422473a14833e4d60f29fa21fa1e0c2396e607aaff7d7401ec2fa3f' 
  AND token = 'gtATExFcKLnTEIsrj66bVS3wlna7HlAKgFg97eAn0G8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}