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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'bd6a3c2c7dfcb2f2c4252a21137a851936345cf3d3404e4fa874fc7fb8e5da0b' 
  AND token = 'vLJ7RPm8+UdVDaSErXM3oMjL4nVr8a3r4GHmxwa5ANI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00043

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}