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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8ef51a10e02a58048f77566d15b14904e0e310623a4ff25c2ff5909aac5d8b28' 
  AND token = '5SMDzNVMbe15jXpzCtiU4qfhIbJw389N72U5arOwkpE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00043

JSON explain

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