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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6df8c10c7b6a0f0866e31ae7ba20cba59bc1607bc7d7fbf2805baa7ecb86b99' 
  AND token = 'mG2f448BWhC8ehG/gIqjzM9+M1joyUEP3m5cMNtESEo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00015

JSON explain

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