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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e3c3fff94951bb21e30ed2f7802bbdc358cf34459be4ec2bbf394bce5985f3a9' 
  AND token = 'y3Tf3H4wTmAlvjEq3Tk9klMHwvAE/F3k07NWCqXZI2o=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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