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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b4627d1080ac0199a6173207be75ba3aa4fe28d09f97d84f812d285f254fc52f' 
  AND token = 'Rjxpr/ByNsfyYpaaYHtk9/2VYGuOiIcaW9+8Wi+ruQQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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