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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '300a1de65df496065e3c54b58330efb888e84adcb0a5e29a887dd710a576da39' 
  AND token = '+mXj4H9jWd+fd43ygv5kmLxcuXsXMDffKB87gWAALRk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00045

JSON explain

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