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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fa15c21a3b3358ed0960cdea42fdfaca0eae0f39dde5b423807ed0b47d26959d' 
  AND token = 'Tk9O5mywC+p3Y9vb4mnzKluPNCi4k4yKdHMjoMgDs/g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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