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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '878912e93b5fab6cc1ab199f33e4f02d20e18e52fe3c0c0e13c3f3c803a2e32b' 
  AND token = 'i/SCZn3dvdlieqVk1mKt+Zhf6dlUhhTfD7O6Lu630pA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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