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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fe7ef7ff80d1f54f5e64b688334d6d3a0b803b640eff4766f254025479cee36c' 
  AND token = 'mns5upBRQivAxE+OamF44JmrN01IWqXitwxCRGH2+WY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00047

JSON explain

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