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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b3875bc6a09366fbfa982cdd8b0f6a08a5c7e0c3c2febcac907dcb0644a2e231' 
  AND token = '0LpeBOYVzaD1AfQnGIj5qkwpBlJzRAdibQegfkXaP6c=' 
  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"
    }
  }
}