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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '39f3cdde03131fb6bfa2f85c823a50c3f175494d913c569b41c64d84684ea1a1' 
  AND token = 'nlb/y0VLugoYegJMtqsWvp5oUwfk+krADNiq9UUpAUs=' 
  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"
    }
  }
}