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SELECT 
  1 
FROM 
  cscart_aprillock_keys 
WHERE 
  key_id = '51fdcca7cbb68b8e8a7230a5cd3be1d4b00deb9211160d69d7d6e064a9a61ae8' 
  AND token = 'fU5TLAv9FOcvuZ2xBmMcs5WQYWwKNBA4rkR7KXeA3fM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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