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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b5820a82c065621defc80ef59b2f6965e89e84fbfc1f847e9c4daa3ee16eb165' 
  AND token = 'P5QJ3ZIvFv20/z9aFosEckK2vOd5AmD+xn11aSMMMg8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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