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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3b90f9e05bfdad196415072280373c6086e34b2f0576a213b98c24196bae1e90' 
  AND token = 'obmg1xN4jomNurmArZ4r14x8uLjcDttgNVfY+l3NDbU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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